I hesitate to post this as it's so vague . . . Yesterday I noticed that an image field on a custom content type had disappeared. (This is outwardly similar to issue Some Content Type Fields Disappeared?) The field had disappeared from the user's and editor's points of view, and from the admin's content type's Manage fields and Manage displays forms. However, the expected JSON files in the active config folder were present (that's to say field.field.field_xxx and field instance JSONs). In addition, there was data in the database for two of the 625 nodes of this content type. Fortunately, I hadn't started to populate that image field for the remaining nodes.
At the same time, the custom shortcuts on the admin's nav bar disappeared, although I haven't scoped that as they're easy to re-build.
I'm reluctant to start getting images into these nodes until I can better understand causes.
I don't recall doing anything that might have triggered this loss. There was nothing informative that I could see in the log. Any possible pointers, please? (Backdrop 1.27.0.)
This is very helpful indeed. Thank you. Yes, I clear caches often when working with Backdrop, as with Drupal too. The menu_router table looks fine, not that I can see inside the BLOBs. It seems similarly tidy to the other Backdrop sites I have installed (this being local for the moment).
I'll go the Devel way for the moment and keep an eye out for this happening again.
Very helpful contribution, argiepiano. Thank you.