flexform sheets are not modified during upgrade
TYPO3 plugins using flexform sheets do not work any more after an upgrade from TYPO3 8 to TYPO3 9.
The reason are the modifications in the flexform sheets. "s_general" has been stored as "general" in flexforms before TYPO3 9. With TYPO3 9 they must be stored as "s_general".
The upgrade wizards forgets to modify the flexform sheet name and add a leading "s_" to them.
#3 Updated by Franz Holzinger 8 months ago
I did not make further investigations about TYPO3. I just have discovered (after several days of bug tracking) that the storage format did change for the extension jf_multicontent.
Other extensions are not affected, because they use different names for the sheets inside of the flexforms.
If you could leave this issue open then other extension authors might find it useful.
And it is not about TYPO3 9, but already for TYPO3 6.2!