Would appear that the undo bug is back.
2022.2, I keep losing my undo buffer.
Noooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
Seriously though. When will this go away?
I think I have mentioned this on Facebook, but this might not be a bug. Some operations need to flush the Undo stack for the software to work properly. Generally we display a dialog warning you of this situation, but there might be some instances when we do not. The best thing you could do is to post the application log or send it to support when this happens.
Thanks @fredwarren for jumping on to explain.
It might be a tricky one to report since it causes no crash/error log. I think I understand the need to flush the Undo stack. It canāt store an infinite amount but not once have I ever seen a warning dialog (Flame 2020.3.1)
The bug is more nuanced, for me, than just loosing the ability to undo. It will occasionally undo something further away. It might jump me out of the current batch and undo something in a different one. I can quickly redo redo redo like crazy incase it has done something I will regret and I restart the software.
I would love to hear from anyone else who experiences this undo bug and how it effects them.
A) I wanted to give you an example of the software warning you that it will flush the Undo stack and I thought about deleting a layer in Action. The problem is that it is not an instance where the software warns you but an instance where the undo buffer is flushed without warning you 
As for why we need to do itā¦ in that case it is because the Delete operation itself is not undoable so having operations made on the Action Media Layer itself (Slip, Blur, etc.) cannot remain in the undo buffer. Otherwise the software would try to undo an operation on an object that no longer exists and that would create problems.
B) Undo making the software ājump outā of an area is by design. That should happen when the operation you are undoing was made in a different area than the one you are in. For example, if you make a modification in Batch, switch to the Timeline tab and then Undo the software will automatically go back to the Batch tab. This is a way to warn you that you are making an operation that affects something that was not on-screen.
Finally, about some operations being skipped when you undo, keep in mind that not every operations are added to the undo stack. This may explain why you think some operations are skipped. one other thing could be that you are using python scripts and that not every operations in a script are undoable.
Hi Fred - Just raising this again as, while I have seen this happening in every version since it was brought up here, I am noticing this issue more in 2026.2 and wondering if others are seeing the same.
Similar to what Rich mentioned - sometimes the undo stack will just completely clear. Other times it seems (from a userās pov) that at some point the undo stack process has stopped removing the earliest operation and started removing the most recent. So regardless of what has caused the buffer to clear or whatever, it doesnāt add any new operations to the list. e.g. just now Iāve been warping a clip in action with a deform mesh - multiple keyframes . On the final frame I accidentally somehow reset the entire deformation (no deforms, no keyframes) but upon going to undo this accidental key press, nothing. None of my warp moves recorded, and the stack has reverted to somewhere way back in the session. No warnings. Critically, when I start rebuilding that warp again (start moving tangents), a keyframe is created but the new move is not recorded in the undo stack as would regularly happen - the undo stack remains ālockedā to what it previously had in it and I am now in a state of āno undos givenā. i.e. I can continue to work as normal but without a backstop - until I restart the software. Itās happening around once a day. This definitely feels like a bug.
Yep. Undo is broken and has been for ages. Many issues besides the buffer.
This is the kind of problems that needs to be investigated by one of our support agent. Please contact them as this is not something we can easily reproduce in the development team without further investigation.
Iāve seen this happen many times, but not every day and never have been able to find the root cause as it seems random (nothing is eventually) .. Because when it happens I donāt immediately notice it until I need undo and then I might have done many other things that obscure the āreasonā .. I think the only real way to track it, is a special build that continuously tracks āclicksā vs āundo buffer buildupā they should be in sync.. and when they donāt.. that should tell us something. If that makes sense?
Thanks, will do. Although that does go against the grand Flame Artist tradition of putting up with something for years just so we can complain about it all the time. Will try to gather as much info as I can next time it happens. As Ton says it does seem to happen very randomly.
Iām struggling with this issue almost daily at the moment. I have no idea how to replicate it and the only way to know its happening is to to continually check the undo buffer in between every other click. Generally speaking it happens when the system has been on for while, not at the start of the day. It happened today when I accidentally severed a whole bunch of batch node connections.. :-/ Because of this I have taken to periodically checking the undo buffer and any time it looks dicey Iāll quit out and relaunch Flame.
Yea, This bug is a constant problem. I think the biggest problem is there is now way to tell whats causing the problem since you donāt know a problem has happened until you try to do an undo and it doesnāt work. And sometimes when you start doing undos it will start doing undoās from some random place 20 steps ago.
I always quit and restart just before setting off a big batch, but as you can see, I reported this nearly 5 years ago!
I noticed indeed that if you click on the reset button above undo/redo in Batch then it gives that warning about the undo/redo stack, only on specific nodes.
For example:
I put a 2d transform, press reset, and it just resets to default values while keeping the undo stack. But when I do the same with a Text node, if gives the warning. And then the whole undo stack is gone. IMO it should only put the Text node to default value (which it does), but also it clears the whole undo stack. I donāt know why.
But another bug I have some times indeed is when the Undo stops working all together, which also I canāt replicate. Only restart software works then.
Im in flame 2025.2.2