Encountering a strange error?

I randomly often every 20-30 minutes get the following error in the screenshot. What can it be and how can I remove it? I know that I made a variable called "Key" not "key" in a previous save but then deleted it as I was no longer using it.

I am also using the latest beta build, R150.

Any suggestions?

Thread moved to Construct 3 section of forums.

— any ideas? (Also the error report should be clearer than this)

Sorry for the wrong section I was browsing the forums.

I am afraid this is as clear as I can put it... I was working last night all night on this specific project and did not get this error, on build r150, Only this morning when I opened this project it randomly started happening, This seems to happen like really random and at unpredicted times.

I don't even have the slightest clue what this might be.

I think this is related to whatever the bug is with browser saves at the moment. There's some issue where we are losing metadata related to projects stored in the browser save file system. The "key is not defined" is an error which should be fixed in the next release that is in the recovery system that prevents file objects with no meta from being lost. I guess this is happening "randomly" because the user has the back up location setting set to "Browser". As for the unhelpful error message from the save system; I had thought that those errors wouldn't be appearing anymore in r149+ but I guess I missed one of the places the error messages are being inspected.