Hello whoever is reading this. So basically I was using renoise as normal, and all of a sudden it just starts to lag (like fps drop), my cpu usage is completely normal (1%), RAM usage is great too. I tried to reinstall it, deleted all files and folders associated with renoise, and finally reinstalled renoise. It worked as it should, nothing lagged, everything was fine. After 10-15 it suddenly starts to lag. I had 0 tools installed, 0 vsts enabled, nothing, and it just drops fps.
Maybe someone had the same problem? How did you fix it?
What does it says in the gui tab of the preferences in Renoise? Does changing the buffer size of your audio device make a difference? Try to A B settings to compare behaviour.