Tensioner bouncing after replacing

Hey guys. I've got Passat 2004 1.9 TDI PD and tensioner for alternator and power steering failed. I've replaced it with both new belts. I've noticed new tensioner is bouncing 1-3mm on idle. Any suggestions please? I have checked alternator clutch pulley it is free spin in opposite directions and locked at direction of engine spin. Could it be that's on the way out or anything else that could cause it?

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Updated. I've tried to replace alternator pulley however could not get it off no matter how hard I've tried even alternator off the car and impact gun it was solid. I was confident that is the problem as alternator pulley had a wobble. I've replaced the entire alternator and the problem is still there. Pulley vibrating a bit about 1-3mm on idle. I'm starting to think that that's normal now. Only thing that's original there is power steering pump and fan. Any ideas??
I've just asked mechanic who said this is normal. It is vibrating up and down not side to side.

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