stop the scroll line from scrolling if the block is crossed

I have 3 blocks, the second block has a line and a scrolling circle. The circle will scroll along with the main scroll, and when the scroll stops, the circle sticks to the nearest point, which is in the center of each block

But I have such a problem here, when the main scroll crosses the second block, the circle stops scrolling and behaves incorrectly on the page

Is it possible to complete the script so that when the main scroll crosses block2, the circle will automatically stick to the last case and stop scrolling at all? And when we rise back and cross block2, then, accordingly, it should work again

In general, the problem is with the last case, when the scroll reaches it, the circle does not move further, maybe there is another option how to fix it, and not the one I suggested

I need the scroll to be smooth from the beginning of block2 to the end, and when the scroll stops, the circle should stick to the center of the nearest case

In my example, this is what happens now, if you stop scrolling, then it sticks where it needs to, but it doesn’t scroll correctly to the end for me

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const circle = document.querySelector(".circle");
const cases = document.querySelectorAll(".case");
let timer = null;

const detectCase = () => {
  const circleCenter = circle.offsetTop + circle.offsetHeight / 2;
  let activeCase = null,
    minDist = Infinity;
  cases.forEach((elem) => {
    const caseCenter = elem.offsetTop + elem.offsetHeight / 2;
    const dist = Math.abs(caseCenter - circleCenter);
    if (dist < minDist) {
      minDist = dist;
      activeCase = elem;
    }
  });
  return activeCase;
};

const handleScroll = () => {
  const {
    height: blockHeight
  } = document.querySelector(".block2").getBoundingClientRect();
  const maxTop = cases[cases.length - 1].offsetTop;
  const minTop = cases[0].offsetTop;
  let {
    height: startTop
  } = cases[0].getBoundingClientRect();
  let scrollDist = startTop / 2 + window.scrollY;
  scrollDist = scrollDist > maxTop ? maxTop : scrollDist < minTop ? minTop : scrollDist;
  circle.style.top = `${scrollDist}px`;
  circle.style.backgroundSize = `15px ${blockHeight}px`;
  circle.style.backgroundPosition = `0 ${-scrollDist}px`;
  if (timer) return;
  timer = setTimeout(() => {
    const active = detectCase();
    const activePos = active.offsetTop + active.offsetHeight / 2;
    circle.style.top = `${activePos}px`;
    circle.style.backgroundPosition = `0 ${-activePos}px`;
    circle.style.transition = "0.5s";
    timer = null;
  }, 800);
  circle.style.transition = "";
};

const handleWindowSize = () => {
  if (window.innerWidth >= 991) {
    window.addEventListener("scroll", handleScroll);
    window.addEventListener("resize", handleScroll);
  } else {
    window.removeEventListener("scroll", handleScroll);
    window.removeEventListener("resize", handleScroll);
  }
};

handleScroll();
handleWindowSize();
window.addEventListener("resize", handleWindowSize);

<!-- language: lang-css -->

.block1 {
  height: 200px;
  background-color: gray;
}

.block3 {
  height: 600px;
  background-color: gray;
}

.block2 {
  height: 100%;
  position: relative;
}

.block2,
.block2 .circle {
  background: linear-gradient(214deg, rgba(79, 142, 255, 0) 0%, #4f8eff 10%, #f5e550 90%, rgba(79, 142, 255, 0) 100%) center/3px calc(100% - 100px) no-repeat;
}

.block2 .circle {
  width: 15px;
  height: 15px;
  left: calc(50% - 8px);
}

.block2 .circle,
.block2 .circle::before {
  position: absolute;
  border-radius: 50%;
}

.block2 .circle::before {
  content: "";
  inset: 3px;
  background-color: white;
}

.text {
  text-align: center;
  padding: 200px 50px;
}

<!-- language: lang-html -->

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.0/css/bootstrap.min.css" integrity="sha512-t4GWSVZO1eC8BM339Xd7Uphw5s17a86tIZIj8qRxhnKub6WoyhnrxeCIMeAqBPgdZGlCcG2PrZjMc+Wr78+5Xg==" crossorigin="anonymous" referrerpolicy="no-referrer"
/>
<div class="block1"></div>
<div class="block2">
  <div class="circle"></div>
  <div class="case">
    <div class="row">
      <div class="col-5 text">Text 1</div>
      <div class="col-2"></div>
      <div class="col-5 text">Text 1</div>
    </div>
  </div>
  <div class="case">
    <div class="row">
      <div class="col-5 text">Text 2</div>
      <div class="col-2"></div>
      <div class="col-5 text">Text 2</div>
    </div>
  </div>
  <div class="case">
    <div class="row">
      <div class="col-5 text">Text 3</div>
      <div class="col-2"></div>
      <div class="col-5 text">Text 3</div>
    </div>
  </div>
</div>
<div class="block3"></div>

<!-- end snippet -->

If i'm understanding your problem correctly, I think you could just add the half height of the last case to the maxTop calculation like this:

  let {
    height: lastCaseHeight
  } = cases[cases.length - 1].getBoundingClientRect();
  maxTop = maxTop + (lastCaseHeight / 2)

This way the maximum top position for the circle will be at the middle of the last case. Please check the updated snippet:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const circle = document.querySelector(".circle");
const cases = document.querySelectorAll(".case");
let timer = null;

const detectCase = () => {
  const circleCenter = circle.offsetTop + circle.offsetHeight / 2;
  let activeCase = null,
    minDist = Infinity;
  cases.forEach((elem) => {
    const caseCenter = elem.offsetTop + elem.offsetHeight / 2;
    const dist = Math.abs(caseCenter - circleCenter);
    if (dist < minDist) {
      minDist = dist;
      activeCase = elem;
    }
  });
  return activeCase;
};

const handleScroll = () => {
  const {
    height: blockHeight
  } = document.querySelector(".block2").getBoundingClientRect();
  let maxTop = cases[cases.length - 1].offsetTop;
  const minTop = cases[0].offsetTop;
  let {
    height: startTop
  } = cases[0].getBoundingClientRect();
  
  let {
    height: lastCaseHeight
  } = cases[cases.length - 1].getBoundingClientRect();
  maxTop = maxTop + (lastCaseHeight / 2)
  
  let scrollDist = startTop / 2 + window.scrollY;
  scrollDist = scrollDist > maxTop ? maxTop : scrollDist < minTop ? minTop : scrollDist;
  circle.style.top = `${scrollDist}px`;
  circle.style.backgroundSize = `15px ${blockHeight}px`;
  circle.style.backgroundPosition = `0 ${-scrollDist}px`;
  if (timer) return;
  timer = setTimeout(() => {
    const active = detectCase();
    const activePos = active.offsetTop + active.offsetHeight / 2;
    circle.style.top = `${activePos}px`;
    circle.style.backgroundPosition = `0 ${-activePos}px`;
    circle.style.transition = "0.5s";
    timer = null;
  }, 800);
  circle.style.transition = "";
};

const handleWindowSize = () => {
  if (window.innerWidth >= 991) {
    window.addEventListener("scroll", handleScroll);
    window.addEventListener("resize", handleScroll);
  } else {
    window.removeEventListener("scroll", handleScroll);
    window.removeEventListener("resize", handleScroll);
  }
};

handleScroll();
handleWindowSize();
window.addEventListener("resize", handleWindowSize);

<!-- language: lang-css -->

.block1 {
  height: 200px;
  background-color: gray;
}

.block3 {
  height: 600px;
  background-color: gray;
}

.block2 {
  height: 100%;
  position: relative;
}

.block2,
.block2 .circle {
  background: linear-gradient(214deg, rgba(79, 142, 255, 0) 0%, #4f8eff 10%, #f5e550 90%, rgba(79, 142, 255, 0) 100%) center/3px calc(100% - 100px) no-repeat;
}

.block2 .circle {
  width: 15px;
  height: 15px;
  left: calc(50% - 8px);
}

.block2 .circle,
.block2 .circle::before {
  position: absolute;
  border-radius: 50%;
}

.block2 .circle::before {
  content: "";
  inset: 3px;
  background-color: white;
}

.text {
  text-align: center;
  padding: 200px 50px;
}

<!-- language: lang-html -->

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.0/css/bootstrap.min.css" integrity="sha512-t4GWSVZO1eC8BM339Xd7Uphw5s17a86tIZIj8qRxhnKub6WoyhnrxeCIMeAqBPgdZGlCcG2PrZjMc+Wr78+5Xg==" crossorigin="anonymous" referrerpolicy="no-referrer"
/>
<div class="block1"></div>
<div class="block2">
  <div class="circle"></div>
  <div class="case">
    <div class="row">
      <div class="col-5 text">Text 1</div>
      <div class="col-2"></div>
      <div class="col-5 text">Text 1</div>
    </div>
  </div>
  <div class="case">
    <div class="row">
      <div class="col-5 text">Text 2</div>
      <div class="col-2"></div>
      <div class="col-5 text">Text 2</div>
    </div>
  </div>
  <div class="case">
    <div class="row">
      <div class="col-5 text">Text 3</div>
      <div class="col-2"></div>
      <div class="col-5 text">Text 3</div>
    </div>
  </div>
</div>
<div class="block3"></div>

<!-- end snippet -->