Image thumbnails sometimes in backend not shown
Sometime the image thumbnails in the page module are not shown in the TYPO3 backend.
The reason for that could be missing reference count values in tt_content.image.
A work-around is to update those counters in SQL (don't use if workspaces are enabled and used):
SET image=(SELECT COUNT(*) FROM sys_file_reference
WHERE uid_foreign = tt_content.uid) WHERE uid IN (SELECT uid_foreign FROM sys_file_reference);