It's weird because this behavior is so inconsistent. The first few battles they behaved normally. Then they were hostile during the battles. The last battle I had, they were friendly until immediately after the battle ended upon which they turned hostile. I made sure not to use AoE attacks during that fight so I know that wasn't the issue.
Yes , got this problem also.
I managed to have 1 battle with them being friendly, after the battle back to hired enemies...
Strange thing is i havent seen this bug reported in the bug section