Yeah, I dual boot. I think my efi partition is around 100mb. I forget if Arch puts just one backup kernel in there, but I feel like I saw a lot of garbage in there once that I had to clear out. Maybe that's the problem, will investigate, thanks.

Yeah, 100mb has been insufficient for some windows updates for me in the past. New windows installs create a 500mb EFI, but Windows 7/8 created a 100mb EFI and kept it if updated to Windows 10. Unfortunately resizing it is a pain, as the EFI partition is normally before your Windows partition.