I sent a support email about this but also figured I would post here in case anyone may be experiencing something similar…
I too was experiencing the issue of disappearing taxonomy boxes with the 5.2 release. I have since updated to 5.2.1 and that issue seems to be resolved but I am now experiencing another issue in that all Field Groups are displaying on all posts despite the rules I have in place for certain ones to display for certain post types.
Check out the attached screenshots so you can see an example of whats happening. I have tried the following:
1) Deactivating and reactivating the plugin
2) Re-uplaoding the plugin via FTP
What is also weird is that I am only experiencing this issue on the site currently being worked on online (hosted with Bluehost’s Optimized WordPress hosting package) but I am NOT experiencing it on my local dev install of the site.
Wanted to quickly follow up on this… while trying to debug on my end I enabled WP_DEBUG in the config file on the server but did not see any errors come up and then once I disabled (set it to false) and re-uploaded the config file, the issue outlined above seemed to have fixed itself. So I guess this can be marked as resolved?