Having said that, the amount of UI errors is just endless. Thank heaven, it's only UI errors.
Using latest Win10, latest MM5 beta, FullHD.
1) "Pos1" - naming of upper most tree node has been Pos1 since the first beta. Should be something meaningful (not a cryptical keyboard key's name), e.g. "Home"
2) mouse wheel scrolling down doesn't work for the main panel's "album art" panel (album art, song text, scroll bar won't move when mouse over mouse wheeling)
3) Right now, several menu entry actions will only result in a tiny rectangular orange colored window displaying "options", the size of the word "options", e.g. View->Layout or Extras->Options. Didn't do that before, can't reproduce.
4) Using the main window's "full window" icon action and going back to "normal window" will make the bottom panel disappear (menu option stays active/checked, unchecking and cheking again will make it appear again).
5) Selecting View->Visualisation will either do a) nothing at all b) showing visuals in bottom right panel or c) full window visual, seems to be by chance IMHO.
6) Minimizing and reopening MM5 window will sometimes result in an after-0.5-second-resizing of the window of about 1 Pixel, hard to tell, sort of flickering.
7) right panel, showing "now playing" (upper panel) and song info (lower panel) and pressing the hide right panel icon, the show right panel icon, will make the "now playing" disappear, showing only the song info. I have to repeat this to show it again. I guess this is intended?
Changing "image size" to some value eg. 200%, this afternoon, saving, then changing back to 100% led to a big multiple lines script error window. I was offered to submit a bug report, which I accepted. MM5 froze at 0% of submitting, so no bug report or error log.