(EDIT- This quit working, was only a temporary fix)
Just had this issue for the first time in FL Studio 21. I went into SD3 > Settings Tab > Performance > CPU Cores > 1 (Dropdown Menu) > (Changed from 1 to 8)
This solved my issue, depending on your CPU the core number may be different. This also may not solve your problem, if your project is already CPU intensive. Potentially you could save a copy, delete all instruments except drums, do my fix, and finally bounce drum tracks out. Or bounce everything BUT drums INTO the track with SD3.
This post was modified 2 years, 4 months ago by Chalopagus.
