It sounds like something isn't right inside anymore. It's time to remove your fork so you can check all the parts. It may be that the original parts had not totally seated for some oddball reason and on top of that perhaps the steering tube is a shade too long so the cap is bottoming on the top of the steer tube. Start by taking off the cap and check that. The stem should be an 1/8 inch or so higher than the end of the steer tube. The shop may not have used the correct spacers for some oddball reason. They and you may have got away with it at first but now that whatever settled in now it's too close and the cap is bottoming. It's either this or one of the bearings has failed in some manner or a cup has cracked, or a host of other possible things.

So either take it back to the shop if it's under warranty or have a go at looking things over yourself if it's not under warranty or you just want to know what's going on.