This seems to be similar to the one previously reported on github #674. I inadvertently commented on that closed item.
From the UI perspective, the fourth mount/vault unlocking completes without error, but the folder reveal shows the empty mountpoint directory. I’ve tried this with a user specified mountpoint as well as one selected by cryptomator. This happens if the volumes are both local disk or a cloud drive.
When looking at the system with df and mount, I don’t see an entry for the 4th volume. However, when I lock one of the first three vaults, the fourth one will mount, and will show up on df/mount. If I quit cryptomator, the 4th will show mounted from df, but will have null stats and be an empty directory. Trying to access it will yield an “Device not configured”. If I mount the 4th volume via DAV, it works ok concurrently. (Did not require restart).
Logs did not yield a stack trace.
OSX Mojave 10.14.1 and High Sierra 10.13.6 both seem to have this issue.
Any help appreciated. Thanks!