Hello,
I just got back my Phantom 4 Advanced controller from DJI. I swear the antennas on these P4 controllers are very brittle. Both of mine broke off at the base of the controller. I tried to replace them while carefully watching youtube videos. I ended up tearing the ribbon cable you are likely talking about.
I sent mine to DJI. They were quick to diagnose the issues and charged me $77 to "fix it". I shipped it to them (they will email you a pre-paid shipping label so you can drop it off at a UPS store.). Three days after dropping it in the mail, I got a response detailing the parts to fix. I agreed and they sent it back. Total time, from me mailing it to them and DJI fixing and sending back was 9 days! I was surprised...but not when I opened up the box...they sent me a BRAND NEW GL300C, version b remote. I linked it to my P4A and it works great.
It's the second time I've used DJI and they simply sent me a brand new "unit". The other was a Mavic Air, and they sent me what looked like a new drone. Different serial number....I cannot say 100% it was new. But, the remote they sent back to me was new.
I've heard people describe bad situations regarding DJI repair service, but I guess I'm lucky. They've always been quick and reasonably priced... They were also quick to respond to emails as well.
You should seriously consider sending your remote to DJI. I wish I'd done that earlier than trying to fix it myself. That was a frustrating thing. Nice peace of mind that you'll get your controller back working as good as it did on day one.