Transcoding fails when using an external database

[Deviant0ne]

As the subject states, I am experiencing an issue where if I'm using an external database (I've tested with MariaDB 10.2, MySQL 5.7 and PostgreSQL 9.6) and I attempt to transcode from FLAC to MP3 (using either FFMpeg or FLAC + LAME), the song will not progress to the next track. If I revert back to the "internal" Subsonic database engine, transcoding works fine.

Running Subsonic stand-alone (6.1.1) on FreeNAS 11 inside of a jail with Java 8 update 131.