Windows 7 :)
I try later on my newer pc, that one runs W10 and let you know.
7! Ah, yeah, I'm sorry I don't have anything set up to test on anything but my personal rig. If I can figure out a nice way to virtualize older Windows versions and do some light testing, I'll try to do so for the future. I appreciate learning of the issue, but I'm not sure I can offer a Windows 7 solution. I'll ask the Pico8 community for advice, just in case.