All events duplicated in Google Analytics 4 Debugger

When running the Debugger via Google Tag Manager and checking the Debug view in Google Analytics 4, everything looks fine... and then all of the sudden, multiples of every event show up. Sometimes there are 2 instances of events, sometimes 3, sometimes more if I stay on the page long enough. And then, sometimes if you reload the page, it will look like they went away. But then it will come back once it reloads again. I was made aware of the issue because a Conversion we have set up to fire on a page_view event (via a GTM trigger) has fired many times, when we only had 1 actual entry. I want to also note, this is happening for both built-in automatic events, and custom events I'm sending via GTM.

Other details:

• We have Google Ads connected directly to Google Analytics 4 via the "Google Ads Links"
• We have Google Search Console connected to Google Analytics 4 via the "Search Console Links"
• The setup is fairly basic/standard - nothing crazy with the setup.
• I have GA4 installed via Google Tag Manager.
• All the parameters in the duplicated events are the same as each other

Here's a screenshot:

Duplicate events in GA4

Here's what I've tried:

• Swept the site for multiple installations of GA4 and GTM code
• Installed Google Analytics 4 directly into the site
• Tried with and without all filters (I had a debugging filter, and Internal filter blocking IP set up)
• I've tried installing GTM using a Plugin, and hard coded it into the header.php file (with and without GA4 installed directly.
• When I pause the Google Analytics 4 configuration tag in Google Tag Manager, the Google Analytics pageview doesn't fire, but the automatic & custom events do. The issue still persists - all events that do fire, fire multiple times.
• I made sure there are NO events that were created in Google Analytics 4 manually - all events are created in Google Tag Manager
• GA4: "Collect Universal Analytics events" is toggled OFF
• When selecting the Google Tag from the GA4 interface, the GA4 property AND the Google Ads account are set as "Destinations". And "Ignore duplicate instances of on-page configuration (recommended)" is toggled ON.

Good question. I'll use this as a future reference for similar questions, so I'll keep it a bit general and sometimes overlapping with the debugging your already did.

In short, don't use the GA4 Debugger. GA4 is a raw product, containing many bugs. The debugger is bugged for now. Some people say reloading the debugger eliminates the problem for a short time, but it doesn't seem to be working for others.

Let's look into the basics of front-end tracking debugging.

There are generally two principally different approaches to debugging front-end analytics: from the tracking side and from the data side. Since GA4's interface is bugged and unreliable, it can easily misreport. I will describe both approaches, starting from the technical one since I usually start debugging from tracking, but if I don't see anything quickly enough, I switch to the data.

Tracking Debugging

Your first mistake is using the GA4 debugger as a significant source of truth. GA4 debugger is a good source of truth, but it's not useful and is generally completely ignored in vast majority of professional tracking implementations. Similarly, for those who use the Google Tag Assistant extension, remove it and in the Future, check the last update date of an extension you're using.

Instead, either use the Network tab with the collect? filter like so:

Or better yet, use Adswerve's dataLayer inspector which looks like this:

In either way, you will be able to see exactly what is being sent on every page.

Now the multiple event firing debugging:

1. Go to the site, check if you see duplicated events firing in the Network/Console. If you don't see double tracking, then either your tracking is fine, or you're looking in a wrong place, like a wrong site or page. Be careful with GA4 events. GA4 molds multiple events into one. It should stop doing that if you look through the GTM preview, but even so, you will be able to see that in the event payload when there's more than one event.
2. Once you find double firing events, go to the Network tab and filter gtm.js. Make sure that only one network request for GTM is sent per page reload.
3. Use your devtools drawer to enable the request blocking feature and block gtm there. Or gtag if you're unfortunate enough to use gtag.js directly for tracking.
4. Reload the page and see if double tracking persists. Or rather if you see any hits to GA4 with GTM blocked. If you do see the hits, it means that besides GTM, something else is doing the tracking in parallel. Likely gtag.js loaded and triggered independently from GTM. That will have to be cleaned up.
5. If you see no GA hits with GTM disabled and see doubles with it enabled, it indicated a problem within GTM, where now you want to open the GTM preview debugger and inspect how many events are firing on page load/page change.
6. Debugging double firing in the GTM Preview debugger should be simple. You just inspect the triggers of misfiring events while having the events they fired on selected (not the summary tab) and it will highlight which triggers triggered. It will also show you the values of all variables on the selected event.

Raw Data Debugging

Now, GA4's UI is bugged. It can easily mislead. And it's still in active development. Google definitely pushed GA4 too early. Its data, however, is quite reliable since the whole data framework was just copied from the time-proven Firebase model. Therefore, I often suggest people to make a free Big Query export of their data and inspect sessions in the raw BQ data to make sure there's indeed double tracking problems. It will become very apparent in BQ data.

In BQ, you want to select all columns where you set a fixed client id (pick one at random if your suspected double tracking is in production), then order by the timestamp to get all hits in the sequence they were tracked. It should become immediately obvious if you have a double tracking problem.

In BQ, it will become very easy to compare all dimensions of two hits side by side. The structure is simple: hits are rows and dimensions are columns. Except the custom dimensions. They're in json, in one column. Just look at two hits that seem like duplicates and compare their dimensions data. That should give more insight into the problem if there is really a problem.

Refresh the debug view page in analytics and see if the duplicates persist.

I have the same issue; the older the event the more copies there are. When I refresh the page everything looks as expected. Then, after some time, they start to duplicate again, including events fired 25 mins ago.

Same problem never seen it happen until yesterday and today. Pretty confident I implemented GTM correctly on the site

Facing the same issue. Started occurring 2 weeks back. Refreshing seems to fix for less than 10-15 seconds in my case.
I was working on debugging duplicate events on my GA4 events itself, and this bug in debug view has only made it harder to find the root cause.