u/Eldrazi

I've 3 red smashers, and 3 of the viper smashers. All but two of them (one viper, one red) have their upper left knee joint hindered. They only bend maybe about 1/3 to 1/2 the way the range they are intended to.

I've tried the boiling water trick to loosen the joints but they will just not budge at all. Anyone have any tips? I assume others must have this issue.