How to:
1. Open REAPER :P
2. Insert a few tracks (Ctrl+T)
3. Scroll the mixer window to view the last track
4. Right click on mixers tab or in titlebar(if is not docked) to get the context menu.
5. Click on "Show multiple rows of tracks..." or "Show maximum rows even ..."
When you scroll back to view the first track all tracks are shifted to the right side.
http://www.raymondjavaxx.com/shared_...-mixer-bug.png
1
P.D. The same thing happens when you resize the mixer window with the view scrolled.