I dont have much ability to reproduce this but it was an odd bug. In editing a measure of a score which probably was half notes under a slur then a tie across the bar line to a quarter note, also under a slur, I needed to edit these notes to make the bar into a whole note. Select first half note, hit my shortcut to double length of note. This created the wholenote as desired but under two slurs. I selected the outermost slur and hit delete. This caused a beachball and then Dorico came back to change the wholenote in that same bar to a breve (double whole note) - within the bar - which is illegal regardless (notes to the right did not move, insert was not on). Then Dorico changed the note again, to a whole note (as if redoing something) and then jumped to a different part of the layout, far away, on its own (maybe to a location of a prior slur, as select often does?).
I was under a time crunch at the moment so I could not take any time to figure out what had happened, other than, to scroll back to that measure, ensure the measure looked ok, and move on. Whatever happened, hasn’t caused other problems so far.
Maybe the layout engine got incredibly confused, attempting to resolve the deletion of a slur under a slur (which is illegal notation anyway and shouldn’t have happened). Maybe the dreadful slowness of my current laptop simply allowed me to see a layout mutation which is normally so fast that it is invisible.