YUP validation on nested object with possible no or more properties

I'm trying to make a yup validation on this object:

placements: {
3: {},
5: {},
6: {0: 'D17'},
7: {},
8: {},
9: {},
10: {},
11: {},
}

The problem is that for example 3: {} could be empty and that is perfectly fine!
But IF it has a kay&value is should check that the string is not empty/length > 0

I have tried so many possible solutions without anything that works.

The object is for saving placements from a leaflet map, if the nested object is empty that is OK, but if the nested object has a key like in 6: {0: 'D17'} the value should be longer than 0 because it will be initialized as 6: {0: ''} or 6:{0: '', 1: '', 2: ''}. We dont know how many key&values it has.

This is the code i have now and its not working at all..

  placements: Yup.object()
      .required("Plassering må velges")
      .test("is-valid", "Minst en plassering må velges", (placements) =>
        Object.values(placements).some((placement: { number: string }) => {
          return Object.values(placement).some((p) => p !== "");
        })
      ),

The problem is that some always returns false on an empty array:

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

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

console.log([].some(() => true));

<!-- end snippet -->

So you'll have to add another check with || (OR):

placements: Yup.object()
    .required("Plassering må velges")
    .test("is-valid", "Minst en plassering må velges", (placements) =>
        Object.keys(placements).length === 0 || Object.values(placements).some((placement: { number: string }) => {
            return Object.values(placement).some((p) => p !== "");
        })
    ),

where the check should be some way of checking that the object is empty. Here I'm using Object.keys and checking if the length is 0 (meaning there are no keys).