Thank you for the logs. It made diagnosis easy.
Unfortunately, the database is corrupt.
Jan 05, 2020 09:30:32.057 [0x7f736cd67740] ERROR - SQLITE3:(nil), 11, statement aborts at 10: [select max(max(metadata_items.changed_at),max(metadata_items.resources_changed_at)) from metadata_items] database disk image is malformed
Jan 05, 2020 09:30:32.057 [0x7f736cd67740] ERROR - Database corruption: sqlite3_statement_backend::loadOne: database disk image is malformed
Jan 05, 2020 09:30:32.057 [0x7f736cd67740] ERROR - Error: Unable to set up server: sqlite3_statement_backend::loadOne: database disk image is malformed (N4soci10soci_errorE)
To recover from this on Synology: