Olivero dropdown not open after Drupal cache clear

I found a possible cause for my problem: the BigPipe module.
If BigPipe is on - the dropdown can't be expanded after clearing the cache.
Wie BigPipe off - everything seems to be fine.

Is this a known issue?

This seems to be a bug report.

If this problem was discovered on a version of Drupal that is not 11.x, add that information in the issue summary and leave the version at 11.x. In Drupal core changes are made on on 11.x (our main development branch) first, and are then back ported as needed according to the Core change policies → . Thanks.

This also needs the standard issue template so progress can be tracked.

Confirming that I'm seeing the same exact issue and that disabling BigPipe does seem to work around it. I haven't been able to dig into the cause but I'd guess it has something to do with the menu JS not handling behavior attachment quite right when BigPipe is sending the page in chunks. Perhaps the menu isn't loaded yet when the JS tries to attach behaviors to it or something.