With the voltage remaining steady and only the amps showing deviation, it might be related to the ammeter shunt connections. Make sure the screws are tight and tug on the wire going into the connectors to be sure they are not loose. If this is it you are lucky, but it is a place to start.
Understanding what wiring scheme is being used would be helpful in determining if a discharged battery is demanding more amperage, It would typically only happen right after start and then diminish as the battery charged. A lead acid battery is assumed.
Did you get a pre-purchase inspection from an RV expert prior to purchase? If so, then anything big and obvious should have been identified already.
is a link to the B&C troubleshooting downloads. They should be a good reference for you.
Did you set the belt tension per the instructions? i.e. static torque to slip the belt? Typically, if the belt is loose, it will slip at times and allow the voltage to drop but will not drop the amps. I can not imagine how it would increase amps as amperage is a result of power demand loads. The regulator is for voltage alone. Just a coincidence.