When not enough memory, Paint.net says "File is corrupt" when opening a second PDN file

[AtomicBlastPony]

I work with rather large .pdn files (often 16k, the ones in question are both 11264x5632 with 12 layers) and it seems to work fine apart from occasional lag when selecting the entire canvas. But today I booted it up and noticed that I can't open a second PDN file if one is already open - it says "File is corrupt or saved in a newer version", but that's clearly not the case because when I open the other one first, it boots up fine until I try to load the first one, in which case it says the first file is corrupt.

If I save the file as a PNG, flattening it, I can open the other file, but if I then click undo, de-flattening the first file, my entire monitor turns black for a few seconds before the program crashes.

After some testing, I figured out that the program is running out of memory, but doesn't communicate it at all. This scared me as I assumed the file was really corrupt and unrecoverable, and then I wasted about an hour trying to figure out what was happening. I fixed the issue by closing some other programs, but a slightly more helpful error message would've saved me an hour of my life.

[Rick Brewster]

Can you share the diagnostics info? Settings (gear icon at top right) -> Diagnostics -> Copy to Clipboard, then paste it into a reply here