Command autocompletion (using tab button) doesn't work properly if you write the first part uppercase. To reproduce the problem, you can simply begin writing a command (like '/SPEC') uppercase in the chat and press tab. I guess it's just because the input is not casefolded before command lookup.

This might be sort-of uncomfortable since Caps Lock switches running. I believe it shouldn't be like that too, but that's a topic for another thread labeled as a feature request.

Fix will be available in 5.12.