Chess game suddenly changes to two player mode in the middle of game

hi,
I am new to trisqul community.I am not sure if this is right way to report a bug. I think, there is a minor bug in chess game. It somehow changes from single player mode to two player mode in the middle of the game. I don't really know how to check source code and change it. But I hope someone would know.
Thankyou,
Manjush