So, I am getting the same error in N12. In N11 everything is fine. (I was not using N12 so much so did not run into the bug so much there)
Regarding the repeat, which might or might not be completely separate issue. After coping an event (midi or audio, using Option+drag) Using the lower right hotspot to size the event repeats the event instead of adjusting its size. Pressing and releasing option returns to the correct behavior for sizing again.
Yes, I know how to engage the solo defeat and how to use it. (I love that the function is there).