The WAL journal mode does not work over Samba. See the first disadvantage from https://www.sqlite.org/wal.html:

> All processes using a database must be on the same host computer; WAL does not work over a network filesystem. This is because WAL requires all processes to share a small amount of memory and processes on separate host machines obviously cannot share memory with each other.

The presence of the `-shm` file is one of the signs that the database is currently operating in WAL mode, and must only be accessed from the machine hosting the database file.

Looking at the list of journal modes supported (https://www.sqlite.org/pragma.html#pragma_journal_mode), you should see if the problem happens with the default `DELETE` journal mode.

Also, see https://www.sqlite.org/atomiccommit.html#_broken_locking_imp... for warnings about the SQLite that ships with macOS.