Undo history failed.

Hi all. Yesterday I was in the process of moving stems from another DAW into a new Reaper session. I had both open, and was writing master buss and group buss (guit, bass, drums etc) automation into Reaper when the undo function failed to work. I would hit command Z, and Reaper would undo, and then not undo. I opened up the undo history screen and could see as I hit Command Z, it would go back a step in history, then just return. When trying to click on an undo point further back in the history, it did the same thing, then flickered. Eventually, it moved back but deleted everything in front of it. It was not good. Does anyone have any ideas? Ski Spiggy

It would be good to have some evidence like project files, videos etc.

I'm not sure what you mean by evidence. Anyway, I have no video of it. I was just working.

For me it looks like a bug, but if there are no steps to reproduce it, then it can't be fixed.

Maybe post a screenshot of undo history settings in preferences?

I can do that.

As I'm using an old version of Reaper, version five I think, I realise I need to update before I can try to sort the problem out.

I recommend you to read the articles about Reaper here:

PS. I really want to make Reaper my DAW. Because for the most part, it does exactly what I need. And I have read many good things about the creator.

Ah. I was not clear enough. That problem track is with Digital Performer. Not Reaper.