Undo suddenly gone

Ctrl+z and Ctrl+Y is very important for me when something goes in wrong way and then I will continuously ctl+z back to the stage that I can go for a better way, but recently when I try to " move backward/ control Z" I found that the “Nothing to undo” appear and I cannot go back.
Re-open the program will have the Undo function back to normal, but all my chance of undo lost when this “bug” appeared.
Can this classify as a bug?

are you on a mac or pc?

what is your setting here? (advanced settings > search for undo)

This is the info. PC

:thinking: This probably happens to me as well. Not often, but time to time.
I noticed that “nothing to undo” is more likely to appear after editing SubD. Rhino Windows.

Hi -
If you have steps that reliably reproduce this issue from starting the PC and launching Rhino, please let us know.
If that is not the case, when you run into this issue, please run CommandHistory, save that to a text file and post that here. Perhaps looking at the lists of recently used commands shows a pattern…

Okay I will try to “catch this bug”, it is not easy, but when this bug comes, I lost my undos.

if you have the RAM, bump up your memory setting by like 4x and change you min undo to like 5

if you are making huge files, it’s not impossible to run out of memory for undo.

Yes, I was working with lots of meshes and maybe the memory used up.

yep. 100% can happen.

crank up your memory available for undo and see if that helps.