Even in the preview version, the albums still disappear when suddenly the server (smb release) is no longer available due to a network error or the interruption of the network. This occurs with both a local sqlite database and a local mysql (Maria DB) database. The error is only noticeable when digikam is opened and then the connection to the network release is lost. At the Next opening, digikam will read the complete albums stored in the network again.
The bug report already exists by the same user. See here: Bug 377849
*** This bug has been marked as a duplicate of bug 377849 ***
Not reproducible with 6.0.0