How to reproduce:
1, new project.
2, add a Drum Machine Designer.
3, add a MIDI Region. Double click to open in MIDI editor.
4, switch on Drum Names.
5, add some notes.
6, move any note up and down, and it is OK.
7, now, drag some loop for this region.
8, PROBLEM: now when you drag any note up and down, it jumps double distance.
Only happens when the region is looped and in Drum Names mode. Switch off Drum Names mode then everything is normal again.