MVC file upload in debug mode causes debug session to end

I have no idea where to begin with this.

I have an MVC website which I made about two years ago. Debugging never presented any problems.

Today I've found that any form of file upload, while testing in debug mode, causes the session to end. Doesn't matter if it's image upload, file upload or what, it always just terminates. The final output in the console is The program '[18876] iisexpress.exe' has exited with code -1 (0xffffffff).

A quick Google tells me that that exit code means 'unknown error', so I'm pretty much lost now.

Anything involving a file upload causes the debug session to terminate instantly. No warning, no error, it just ends peacefully without any hint of what the problem was. The final thing in each case is my clicking on the 'upload now' button. I do that, then the session stops as if it had never been running in the first place.

The only major change I've done at any point is updating to VS2019, but that was quite a while ago. I'm currently on the latest version (16.3.8)

This is a very peculiar error. Anybody with similar experience please let me know!

Thanks