Tried SLKR vs SLKR and both team members were impossible to beat forever. See the attached image. Note that the defending team had new DC level 15 for Night vision Rey. Other counters did not work ...
Ideas
SLKR + Rey mirrors have been an interaction "issue" more than a bug. No one can be killed until everyone takes a turn, and if you're using FOO, he could be reducing an enemy TM, so they can't take a turn. Noted by both Rey's still being under stealth.
Edit: It is Rey that is reducing your TM from her malevent Lineage ability.
You chose a poor team to attack with. Not a bug.