The store swapped the plastic bit many times, like 6 or 7 times. But it keeps breaking. So, here's what I'm gonna do:
When I can, I'll ring up GM to chat about it.
The store changed all the parts except the tailgate itself.
They're stumped. They say it's 'cause the part's no good and it's weak.
They've seen a few break, but I'm the only one with this problem almost every month.
Check this link for GMC Sierra quality products https://www.ecoauto.shop/collections/bullet-antenna