A pinch- will cause a bump in SWR.. and even if i is only 1-2 inches from the antenna. it can have strange effects on antenna performance especially at UHF frequencies..
What happens is that the coax is deformed at that point the coax will heat and further deform, and eventually the shield will touch the center conductor..
Simple disassemble the mount.. 90% will disassemble and resolder leaving the coax about 2-4 inches shorter.
Personally the best antenna mount is a drill through ..
However, I know from experience - you buy a car with a sun roof and drilling is kind of out of the question..
Besides antenna mounts are cheep...
Larry Macionski