[Shifted Music]

Led mentiones noise reduction plug ins some how writing control info which fill undo.. then you video has noise reduction plug in open.

so do the same thing in the video with the info history window open and maybe its the same issue...

and then send the to isotope regarding that..

It seems like since the undo does actually work but only after hitting command z a ton theres something else entering the history making it hard to get to the point of your actual edit which also seems to match what Led is saying...

anyway just an observation since I've never had this issue.