Revision 777 should get rid of the issue.

Still waiting for confirmation... Check out http://sagagames.de/stuff/mptrack.exe

(1.19.00.30)

I finally got the chance (and remembered) to test this...

Test on Note Properties input undo:
I tested the Undo function for entering notes via the Note Properties dialog in an MPTM track. I first double-clicked an event field and selected an instrument at random. Then i went to another row and did the same thing but selected a note FX command. Then again, but for a channel FX command. And lastly, a note with an instrument call. I ended up with:
... 01 .. ...
... .. e00 ...
... .. .. #4A
F-6 06 .. ...

When i pressed the Undo shortcut, only the first entry was erased. Subsequent undo's did not work. After further entries by the dialog, Undo would not work. I also checked the menu in case there was something wrong with the shortcut, but the Edit menu's Undo item was disabled (grayed out).

So after testing, the Undo only works with the first entry from Note Properties, but none after. I would say it's still not working.

Ah, I see what is happening there. I actually wanted to create just one undo point, but apparently that backfired, because the variable for that is apparently not reset properly. Will be fixed in 1.19 Final...

Please check if OpenMPT 1.19 final works as desired.

Yes, works as expected. You may consider this bug fixed.

Good job, and thanks, Jojo! (in case no one ever mentions it;)