TB Display Flashing and Audio distortion

Very intermittently I get a flash of black on the display and then it goes back to normal. Extremely annoying when working. The built in speakers also seem to partly at fault because I get distorted audio when plugging in a USB device like my keyboard and mouse. Here's my setup: Mac Pro 6,1, 3.7GHz, 16GB RAM, 1TB SSD, 2xD500, 27" Thunderbolt display serial #C02NJ125F2GC, extended wired keyboard, might mouse. Tried replacing thunderbolt cable with same results. Computer was just recently serviced. I've noticed the Thunderbolt cable seems to get quite warm when this happens. Possibly a cooling problem with the Mac Pro? Here is a video of the problem in action: https://www.youtube.com/watch?v=cV9Wr3DMsfM&feature=youtu.be