I'm having the exact same issue for months now. Same codes. Would like to know what the issue is as well. What is your full exhaust setup? Also do you use a dp fix?
I've replaced front o2 sensors as well. Also reset lambda and AFR with no luck. Codes come back straight away.
BMW 135i N54
MERCEDES CLA45 AMG
PAST: NINJA 300 ABS, BMW E46