Manual Schedule gets changed to single Episode Recording

[Schulp]

Following happens on a single ATSC tuner system (Mythtv light 0.29):
On one of the retro channels they show three episodes in a row. To avoid having back to back recordings with that single tuner I programmed a Manual Schedule form 12:00 to 3:05PM (actually also starting 1 min early).

Usually the system does what it's been told, but occasionally - and recently more often - it just records the first episode of the three and stops recording (unless I intervene manually). The first recorded episode shows up in the Media Library as if I had requested to record a single show from the Program Guide. It has the episode title and metadata, info that is of course absent if it follows the manual recording rule for recording a three hour block.

In the "Previously Recorded" list the manual programmed schedule shows up marked as "E" (recorded earlier) and the single recorded episode that the system chose to record instead is marked with "R" and also shows episode title there.

I just don't understand what is going on and if the system tries to be smart why it's not consistent and always doing it?