With my LG VX6000, I notice that the signal periodically drops off. It could be during a call or while the phone is idle. I noticed this happens on the VX3100 as well. But it didn't happen when I used the Motorola V60c.
While the 6000 is out for a couple carriers, I assume yours is probably with Verizon. Check the software on the phone (settings, phone info, software). If the software string ends in a "5" run it by a technician to have an update to the "6" version. I noticed fewer variations in the signal one I had this done. By the way, I also have a V60. Its signal never fluctuates, but to be honest the call quality on the 6000 is better. Two bars on the v60 still had a slight scratch or warble to it, while one bar on the 6000 (exact same location) had perfect clarity. Hope this helps.