[schnautza]

I just experienced this same issue yesterday in rehearsal. Didn't think to take a screenshot, should have.

I was erasing some highlighting by drawing the box around the area to erase. After erasing, there was suddenly two parallel straight lines down my page with a red pen (probably red because that's my default pen color?). Also, a portion of the music got covered by a new white-filled box (that's how I like to "white-out" my music, a white rectangle with white borders and white fill)

This did not correspond with the area I was erasing, seemed completely random. Upon undoing and retrying several times, it appeared that the stray new lines were in exactly the same place every time, regardless of where I tried to erase.

The only solution I found was to let it draw the extra lines and white fill, and then use the eraser again to remove the new noise. The second erase in this process did not generate any more noise.

If it happens again, I'll take a screenshot...but I won't be using it again until Saturday this week.