Hi Bernhard,
do you mean bugs in the REST-API or RA-REST agent?
We had some issues with the RA-REST agent recently but the newest version (v4.6.13) fixed it for us.
As AE we are using v21.0.11 and v21.0.9HF1 in production but we are going to update to v21.0.12 because of a annoying bug in v21.0.11 (not active objects are not going to deactivate automatically)
And have you perhaps some details about your bug? :)
Regards
Stephan