Invalid value "FILE" for enumeration "TYPO3\CMS\Core\DataHandling\TableColumnSubType"

[spiegel]

After upgrading TYPO3 from 9.5.21 to 10.4.8 and updating ws_flexslider from 1.5.12 to 1.5.14 following error occurs

[DavidBruchmann]

FILE was removed.
Implementation has to be done with USER and namespaced class if it's about a class-file.
Autoloading will be done by composer even in an installation without composer-setup, so classes never have to be included in TypoScript but just referenced with namespace.

[DavidBruchmann]

10 = USER
10.userFunc = Vendor\Extension\Plugin\MyClass->myFuntion

[spiegel]

On a fresh TYPO3 10.4.9 installation with The official Introduction Package and ws_flexslider 1.5.14 the error doesn't occur and everything works fine!

[Abdul-Hafiz]

In the upgrade project, there should be a field with 'internal_type' => 'file' config in tt_content from any other extension. You need to change the config of tt_content fields.
I have faced issues because of EXT:mediace's multimedia field.

Hope this helps!