New Used engine fault codes P0050 P0155

[anstskpstn]

Hi! I drive 2007 BMW 530.
Just had my engine replaced to a different used one. Once it was done new fault codes appeared P0050 and P0155 + Check engine light is on. Mechanic does not want to take responsibility, says he did nothing that could cause these problems. Can new engine cause these problems if it's bad?
Thank you!

[MIKYZZ4]

Check the fuse for the oxygen sensor heater circuit.

[anstskpstn]

Replaced the sensor, codes cleared but now 5 cylinder misfiring. Compression, spark plugs and ignition coils are fine. Any thoughts what's going on? Thank you