Re: In the moment....transitioning into another technique
We do this sometimes on purpose but with a purpose. Uke resists in the sense of staying well balanced and right on the edge of executing a reversal. This way any form break or loss of connection really makes it hard to do the technique so it is amazingly helpful feedback.
Usually this is done progressively so uke (always an advanced or senior) does this primarily to test the juniors ability and then adjusts accordingly to keep just on the edge of the juniors ability.
If this is done too much or in a careless way it is detrimental so there is a fine line between enhanced learinng and just BS ego tripping.
I always look forward to these sessions with my seniors because it really keeps me honest. I still can't do ikkyu very well even though sometimes I think I can.
The other posters are correct in that one must do as sensei has demonstrated even if sempai are not doing it as you saw you must go with what you think you saw sensei demonstrate. Let sensei give the corrections. You will know when sempai is aligned with sensei in this respect and when they are not and so will they so there is no need to point it out. Just keep trying to do what you think sensei demonstrated.