The bank angles are a function of rate of turn derived from the turn coordinator. First job is to level the aircraft and check that the slip ball is centred so that the TC doesn't give erroneous turn data (the TC has an inclined spin axis so will give a turn output if a bank exists even if you're not actually turning). If the slip ball is not centred, rotate the turn coordinator in the slotted holes on the panel to get the slip ball in the middle. That will hopefully sort all of the problems. To test further, you have to plug in a laptop (connector is underneath the panel by the park brake lever) and then interrogate the maintenance pages to check sensor inputs.