In reading through this thread I only see where some have had success with replacing the Antenna. Has anyone tried an FM booster module like this one http://http://www.bestbuy.com/site/car-antenna-radio-fm-am-signal-amp-amplifier-booster-easy-to-install/1309368020.p?id=mp1309368020&skuId=1309368020
I'm not sure if our antenna's use the motorola type connector, but I guess this is an idea to try.
I also am experiencing intermittent HD-FM reception issues in my 2014 GMC 1500. Have checked antenna for tightness and it was fine. Will mention to dealer upon next visit