i have nearly the same problem, im on Reaper too, allthough its constant crackle in sound

My RME802 sound like an 8 bit in H9000->optical adat connected to my Rme 802 – i think its in the connection… i will check if its “locked” to 44100 khz, and maybe its the (cheap) optical cables…i try XLR analog later 🙂