I observed the same problem with myself...but not with every partner, only with one very special person - my son. It is just not possible to train SOME techniques with him, and these are the techniques neither he nor I master very well.
Finding out that the technique doesn't work with me, he gets aggressive or completely slack, not attacking or defending himself with the most minimal concentration & effort, a behaviour he only shows when training with ME but not with anyone else. Sort of parent-child authority conflict on the mat, very disturbing for all participants. And when seeing his negative attitude, I throw too hard or grip too strong, something I'd never do with any other partner. Obviously, he does the same with me, and when a technique does not work for him, he always manages to transform it into a very vicious sankyo.
I try to resolve the problem by not training these techniques with him (worst is irimi nage), but I am conscient that a better solution would be somehow not to get caught in this stupid fight for power.