Permanent four creatures bug

I encountered a bug in the top node of The Harvesttide that allowed me to have four creatures on the field at the same time -- not just until end of turn, but permanently. It seems to have been triggered when I had two creatures out, then cast Huntmaster of the Fells, then chose to replace the Huntmaster itself with the wolves that were created. The next creature I cast entered the field separately, as a fourth creature, and stuck around. A couple of turns later the game froze, which may or may not be related. My planeswalker was Kasmina. The full deck list is as follows:

The Celestus
Moonmist
Tovolar, Dire Overlord
Arlinn, the Pack's Hope
Huntmaster of the Fells
Temporal Mastery
Void Rend
Brokers Charm
Ludevic's Test Subject
The Kami War