Are you sure it's the middle piece getting loose? I recently thought that was the problem with my phone before I tried to scrape out any lint that might be in it with a pin. Now the cable seats better and it works fine. I think that is a bit of a flaw of USB-C in devices that are expected to be put in pockets or thrown around in bags. It's easy for lint to get in and difficult to get it out without potentially damaging the socket. I wonder if we should have gone with something using a similar form factor to lightning but the speed and charging abilities of USB-C.