I asked this last winter and couldn’t find a way to resolve it so I just deleted Renoise, but now I have a new iMac so I thought I’d try again.
Just installed Renoise - when it opens and it gives the selection of demo songs, I skip that and just let it open the blank song template.
Track 01, 00 - if I hit escape to enable editing, it starts autoplaying and repeats E-3 sample 00 in every slot. Same if I open any of the demos or tutorials - enable editing and it enters notes in every space until I kill it.
Just an iMac, running the latest Catalina, audio interface (Apollo Twin X), QWERTY keyboard and wireless mouse connected, nothing else.