We are facing multiple occasions of shared fields loosing their value on our productive Sitecore 9.3 environment. So far, we where unable to reproduce the issue in a controlled environment so we do not know exactly, when and how the data-loss happens. It can either be when creating a new version of the item or when the item is saved. There seems to be no pattern on when the data-loss occurs (happens about once every few days, maybe more often if the CM server is used by a lot of users) and on which items (happens on items in buckets mostly, but also items that are not organized in buckets).
There are standard fields involved (e.g. "Enable Item Fallback", "Bucketable", " Lock child relationship") but also custom fields from our project specific templates. So far it looks like it only affects fields which do have standard values assigned on the templates (e.g. we enable item fallback by default).
Some information about our solution which may be important: We have a lot of content (about 1 million items in the master-DB) with some items having up to 100 fields, multiple numeric versions and up to 41 language versions. But so far the data-loss happens both with items having few versions as also with items having lots of versions.
Does anyone came across similar issues and/or has an idea what this could cause? So far, our analysis did only result in not finding any potential cause and also not being able to reproduce the issue.