Have faced this issue in a system.
All the APs are running 6.4.0.2_4.1.0.0 and newly purchased APs came with version 6.4.2.3_4.1.1.4. Mismatch issue has happened in my system.
I have duplicated the group and moved new APs to new group and has changed policy version to 4.1.1 and it successfully get the right configuration.
One big question for me is ; what if I changed the original group policy version setting to 4.1.1 when they are running old firmwares ? Is it possible or should I upgrade the firmware ending with a code with "4.1.1" ?