Since this morning any attempt to print certain invoices did nothing. No obvious crash, no errors, just nothing.
I opened the form template editor and printed from the print preview in the editor and got an error there - something about calibri.ttf (the font file) being corrupt. It's not corrupt, but changing the font to arial got the invoices printing again.
This isn't really a fix, but hopefully it helps someone.
The font file hasn't changed recently (dates are like Feb 2025 or 2026 or something), and i've uninstalled the recent update and that didn't fix it either.
I'm uninstalling the recent security update now to see if that changes anything.