This is something that happened while I was searching for another bug so sorry for being a bit orthodox. It is not like it is a beatmaking situation.
In the first video, the repetition of undo/redo after append to self seems to create a pattern in which the copied elements are not triggered in the first 4 bars. (Although they seem to be here in Step program)
In the second video I tried to show what’s happening in the first video. Unsucessfully. As it ends with a freeze, I m putting it here in case it can help