Hi!
When moving a note inside a media item that has
looping source On, you'll have this glitch whenever you have the media item extended to the left and try to move a note from the next repetition.
You can check in the gif below:
Adding to that, you can also notice that if you have a long note with this same situation, you cannot select the note and you can even resize it from the middle of the note:

You can notice that when you ctrl+z the media source length will bug to a different value than what was expected.
And other bug related to that is that you can't select a long note in this previous situation. It seems that whenever you have a note appearing in a fraction of a loop, Reaper will recognize that fraction and understand as if you're trying to move the note from the fraction of the loop, but if you try to move/select the note before the length of that fraction you won't select it.
Sorry for not being able to describe the bug very well, but here's a gif:
Thanks!