Posted by Generic aka RSDuck

the game first writes to the W_PowerForce register and then waits for the effects which includes that W_RFStatus is set to 9. The problem is that once in a while a packet is received inbetween (from the simulated access point) which messes with the W_RFStatus register and the code gets stuck there.

Setting W_RFStatus back to 9 allows to unlock freezed savestates. And desmume hard codes it to always read 9 for the processor. What we don't know is if some setting made would prevent the DS from receiving data or if it's purely by chance that this doesn't happen (as often) on hw.

There's no reason that a recent change made this more likely, though I guess JIT has higher chances for this to happen.