Two things worked for me:
occ encryption:decrypt-all (on one of the server) which safely decrypted all files and disabled encryption in a couple of minutes
on another server, this command didn't decrypt all files but ran without errors, so I needed to come up with another way. So, I put all files and folders into one folder on my laptop, used occ encryption:disable to disable encryption and then created a copy on my laptop, waited for the copy of the folder to upload to the server, then I would delete the original (and rename the copy). Took some time, but it worked.