Scheduling server side M3U breaks playout

While scheduling a server-side M3U playlist in between two mp3 files within the same episode i got the following behaviour:

the first song was played
the M3U containing a single track was played
instead playing the third song fallback was played
afterwards no new episodes where played at all, castor seemed to be in a state where it could not pick up new episodes anymore
after restarting castor it worked again as expected

I cant reproduce this reliably right now. I managed to get that behaviour a second time, but other times it just worked as expected.