Thanks Ian!
Sorry, I had a doctors appointment and I couldn’t make it back in time.
I was able to log-in and check now. The issue is not related to the plugin whatsoever. It took me a while to debug this and it turns out it’s a 3rd party script that basically changes the checkbox states, this one: https://buildreview.org/wp-content/plugins/buildsource_member_notes/buildsource_member_notes.js
When I block the script via dev tools, everything work okay: https://i.imgur.com/UCCb0tq.png
It originates from the buildsource_member_notes plugin directory which is the “BuildSource Member Notes” plugin. The faulty lines seem to be these ones: https://i.imgur.com/CrmEaEw.png
That might be a mistake, but lines 185-187 in that script will change EVERY checkboxes on the page to unchecked states – except for ones with specific classes. I don’t think they meant to do that, it’s terrible.
If you want to keep using that plugin I recommend contacting their support, this issue will affect every single checkbox on your site one way or another. This is why I usually recommend testing issues with every plugin deactivated to make sure not another is at fault, like in this case, unfortunately it happens a lot and I can’t prevent that.
I made a few changes to the search bar as I was debugging, and I don’t remember which categories and checkboxes were selected – sorry about that – make sure to change it back.