Fusion composition suddenly goes black in Edit tab

I have a recurring problem over the months.

I can have any Fusion composition that is on top of a video clip, i.e. not a compound clip,

And it works, i.e. in the Fusion tab's MediaOut, I can see the composition. In the Edit tab, I can see the composition over the video.

Then, suddenly, after working for many days/weeks/months, in the Edit tab the Fusion clip is completely black, although I can still see the composition when I go to the Fusion tab.

Your first reaction is to ask me to send the settings file to check the composition, check the Alpha channel etc - but I reassure you, it not the node-configuration. The problem is random. It happens with complex compositions and ultra compositions. When I go back to backup archive copies of the composition, they work perfectly. It has happened with the simplest of composition, e.g. background-alpha / merge-background-ellipse / MediaOut.

I wondered if anyone has seen this sort of problem before?

No I do not think I have seen anything like this.

When you say that it suddenly stops working - does that mean it stops working without you having recently made any changes to this Timeline and/or this composition? You close the project one day, then when you open it the next day the comp suddenly no longer works?

Or is it being triggered by some kind of editing action - even if it's unclear what that action is?

When it happens, is it just one specific composition, or are multiple such compositions affected?

If you get this again, please make a screen recording showing:

1. Edit page
2. Fusion page
3. Fusion page Keyframes pane
4. What happens if you toggle Playback -> Render Cache -> None

I've had similar issues, everything looks fine in the fusiontab, but render it in resolve and it flickers to black (most often there were trackers involved). Sometimes rewiring stuff solved it (ie connect a tracker direct - not via a piperouter, or use a bg as input instead of unnecessary media...).

Never found a true solution though.

Hi,
had this issue ever since i started to try using fusion.
got it now:
one of my medias were shorter than the total length of the comp
i mainly do greenscreen and the background was too short and rendered black for the end of clip
hope this helps
best