Goldy.
you never got back to me regarding my suggestion up thread.
so i'll repost it..as follows.
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you say that all is good with bb 2020.
thus i suggest that you do the following.
1. go into your bb2020 audio and midi driver settings.
and write down those settings.
2. NOW go into your bb 2021 audio and midi driver settings.
write down the settings once again.
DO YOU SEE ANY DISCREPENCIES BETWEEN THE TWO SETS OF SETTINGS ?
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frankly i wouldnt give up on the rme. its good gear.
(i suspect a settings difference between bb 20 and bb 21
is your problem .)
but if you decide to ; here is a thread i started on pg where many pg users have posted their audio interfaces that work well with pg products.
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=635707#Post635707
i would recommend you rent firstly any audio interface to see its compatibility. thats what i do before buying.

if you feel daring there are also usb mixers you can try like the allen n heath zed series or the soundcraft notepad series etc and others.
best
oldmuso

my songs....mixed for good earbuds...(fyi..my vocs on all songs..)
https://soundcloud.com/alfsongs
(90 songs created useing bb/rb.)