Hey, John!
Managed to fix it! It was incredibly weird, I really don´t know how it happened… My guess is that some settings changed when I upgraded to a new audio interface last week and some settings changed?
It was fixed by going into Studio Setup—MIDI—MIDI Port Setup and Ticking the box Use System Timesnap for “Windows MIDI” Inputs, and un-ticking the box "Use Device “Direct Music”.
It´s a digital Roland piano RP201, connected through MIDI to a Focusrite Scarlett 18i20
I have no clue what these do… but It fixed it 100%!