here's another possible fix for the savegame issue regarding the latest Experimental update. For some of you the SavegameEditor fixed it. It could have been a problem with headers. But this didn't fix it for all of us. So there are different problems.
For the last two hours I was in contact with the owner of this website:
https://ficsit-felix.firebaseapp.com (some of you might know it)
He had a solution which fixed my savegames. There was no header problem on my saves. There was an issue with the railroad entities (which are not in the game right now, but already part of the savegame).
This fixed my savegame!! So this really nice dude added a module on his website (see above) to save the uploaded file again and fix the railroad issue.
This fix isn't garanteed, so make always backups of your savefile.
Upload your save to the website. If you have the railroad problem, the site will give you a warning in a big yellow box.
Click to save the file somewhere on your pc.
Be aware: you can use this savefile now. But if you save it again via Experimental, it will get corrupted again. So for the time beeing (I hope until monday) you have to do the above procedure for all saves you do via Experimental.