And chain breaks model in Chrome

Well, there must be something else, here. ECA has nothing to do with your browser. Your browser shows a form, and the user submits the form. The processing that ECA is doing, is then happening entirely in the backend. That is in no way influenced by the browser.

What may be different is the user session, so that 2 different users are logged in from the 2 different browsers. And those users may have different permissions. Or some other context is different, but nothing from the browser.

If you're uncertain about possible differences, you should use Debugging and compare the logs. This will then expose the reason why the processing succeeds in one case but not the other.

That's the weird part. This particular model doesn't even trigger a log record, either way. I'll try the expert Webprofiler instead.

If there is not even an event being logged, then Drupal doesn't dispatch that event. It's unlikely that web profiler will show anything different.

I found the log - had to tweak the underlying report view to get my date filter to work correctly.

It's definitely working without the AND condition, and it's definitely breaking in Chrome. Best I can tell so far is that the AND condition is loading out of sequence or is disrupting the form submit somehow. Possibly an Ajax conflict on the front end.

Interesting that Ajax is in the mix, that's significant new information. Then you should see something in the browser console and/or in the network tab. Is the request sent? What's the response? Any error messages there?

You can still create a simple example to reproduce the error on a vanilla Drupal site and upload that here for review.

No console or network errors. The network tab seems to be the same with or without the AND join.

I'll post an example when I have time to spin something up. I'll keep fiddling.

Resetting Support Request. Must have responded on a stale form.