Okay i was able to fix it luckily^^
Just duplicated my current sequence in Unreal, then closed it. After that, i put an autosaved file of my sequence next to my original sequencer and opened it in unreal. Copied the Cine Cameras from the Outliner into the Outliner of my original sequence.
Then simply copied the keyframes of the broken cams to the new restored ones. This did work!