Why might Node be unable to read multiple upper case files in a Windows directory?

I have a problem related to a software development library called typescript-eslint, but seems to actually be an issue with Windows (specifically, reading files from a drive).

What's interesting is that the problem happens on one drive (C:) but not my 2nd drive (D:), which indicates it's a problem with my Windows config (rather than the software library).

The issue is that the library can read lower case files just fine:

• foo.ts
• bar.ts

But when it comes to files with upper case chars:

• Foo.ts
• Bar.ts

It's only able to read one of the files.

Related bug report: Bug: AST is undefined on Windows when more than one file with upper-case char in filename

I thought perhaps it might be related to a problem with Windows case sensitivity, so I tried disabling it but that didn't make a difference.

fsutil.exe file setCaseSensitiveInfo . disable

I was about to format my computer, but thought: What if it works on D instead of C?

Works fine on C, but not on D drive.

What could cause this?