macbook ctrl key acts as alt (control/option)

Suddenly when I press my Ctrl key acts as if it were the Alt/Option key. I have not changed any settings though.

I am mapping the Alt key to the Caps Lock key (see image). But besides that everything is standard.

If I map the Ctrl key to the Caps Lock the Caps Lock will act as Ctrl (as expected).

Goolged the problem and could not find anything about it.

Help is highly appreciated. Thx a bunch. (added screenshot with OS & device info)