Big Problems with export (mask)

Hello everyone

i tried to export my Video but in the final export file the Mosaik Mask is not like it supposed to be. (how to see in the screenshots)

In screen1 you see how the final file will look like and in screen2 thats how it should look like.

I tried several things like reset the settings, uninstall the program i even changed the redndering settings to Mercury Playback Engine-Software Only.

Nothing helped at all. I can export other projects without any issues. Yesterday i export this project for the first time without problems, too. Today i added some more footage and now i have this Problem with the masks. I hope you get my problem despite my bad english and also i hope anyone can help me. I need the video to be done asap!

Thanks for every little help!