Connie, first off the impeller should not have been jammed, secondly it sounds like the impeller is either not seated properly or the shaft is bent or the housing is squint. The impeller is easy to get too in an XP3 and its difficult to get it wrong imo, so its probably a faulty impeller/shaft. There could also be something trapped in the impeller housing.
I would take the lid off, remover the impeller, check to see if its straight and all the blaeds are there. Then check the housing that its clear of debris etc, there is a little black rubber cap that goes on one end of the impeller shaft from memory, its used to align the impeller up, check its there. If its not that could be the vibration problem.
If the impeller is vibrating then the flow through the cannister may be impaired. If you have used seeded material in the filter it should perform staright out of the box. If the water is not flowing through the media then the media may now be anaerobic so check it (with your nose...).
Also in the XP3 there is a lid that goes on the top of the upper tray, that has to be in place to deflect the water down the sides of the cannister, otherwise it will take the path of least resistance.
I won't mention eheim
hth,