I had a similar issue with my new Specialized Crosstrail Elite. I absolutely loved the bike but I initially noticed some 'rubbing' of the chain with the derailleur. Over the next few weeks, this worsened such that I had difficulties changing gears. This eventually lead to a subtle oscillation from side-to-side of the crankset (my apologies if I'm getting the terms wrong....). Eventually while climbing up a hill, the entire crankarm fell off. I've tried to attach photos but I see that I have to post >10 times to be allowed to post....

I was pretty disappointed. I never had issues with my 2013 Specialized Sirrus Comp. I went back to the LBS. Over a few hours, the LBS made various adjustments but the bike still didn't feel 'right' on various trials of riding. They eventually appreciated that the side-to-side oscillation was worsening and they discovered that the 'standardized spline' and the 'shoulder stop for the crank arm' were stripped. There were other problems but I'm uncertain of all of the details.

The LBS was quite apologetic. They did not feel that it was an issue of not putting the bike together incorrectly and that it was a manufacturers defect. They offered to replace the entire crankset but I wasn't happy with this solution. They understood my concerns and were kind enough to get me a new Crosstrail Elite. So far, the new Crosstrail Elite has been fantastic.

I hope your LBS treats you fairly. Hang in there and hopefully, this experience doesn't taint your overall enjoyment of this terrific bike. Good luck.