I fixed this by turning of sync on all devices, removed the faulty sync_default.walletx. Turn on sync again. Locks like all changes I did on the devices where synced correct! The error disappears.
When will this be fixed? Same issue here macOS and iOS devices. Access to oneDrive works perfectly but the enPass sync asks "Password of data on OneDrive is required". Please fix that! It's a really annoying issue. Thank you!