TYPO3 Core

TYPO3:
Version 8.6.0, upgraded from 8.5.1 (there this works). Was build with 6.2.x and is now my testing environment for new releases.
Database update completed, only some fields left in DB used by now inactive extensions. DB compare just wants to remove them.
Upgrade wizard also completed (100%).
Content temaplating is done with CSC, but the error occurs also with FSC. There was no content migration until now in former 7.x/8.x.
PHP: 7.0.15

Description:
Only BE is affected, frontend rendering is fine, images are displayed with correct settings/size/position.
The error occurs if I want to add a new image to or just edit an existing file reference in a cObj of type "Text & Media".
After selecting a new image, the sys_file_reference should be created and displayed. Instead of this I get an error 500 - An exception thrown by the core.
The same when editing an existing one. After opening the cObj, I see in tab "Media" the current file references (collapsed). When I want to edit/open one of them, I receive the same error.
Seems like the issue is related to the new crop variants. In my use case not any cropping was used until now.
I have attached the complete exception output as html file - is that ok?