2021 3500 CCLB LTZ tailgate stuck

[ChevyGMCfan]

Hello: yesterday I pushed the button on the tailgate to close it. It went to what I would describe as the "first" latched position and stopped. It isn't completely closed but is latched and won't open or finish closing. When I press the button, I hear a noise from inside the tailgate, but it isn't the sound of the motor trying to pull the tailgate closed, or the click of the latch releasing. Double clicking the tailgate open icon on the remote gives the effect of it trying to work. The owner's manual says: the electric tailgate can be opened if the battery is dead: "contact the dealer".
The battery isn't dead. Since it has power, I'm curious if anyone else has experienced this problem. This is my 14th GM truck but first with the electric tailgate. As a retired automotive tech, I'd like to fix it myself if possible.
I have looked down from the top of the tailgate edges to see if anything is jammed in latches. I have removed the inner access cover and found the latch release pins.

When I double click the fob, they rotate. I have attached cable ties (see photo) to these and pulled both of them at the same time, no success.

Anyone have any experience with this?

 

Thanks, JC

[GMCustomerService]

Thank you for sharing this, J.C. Having a tailgate that won't close or open suddenly can definitely be a cause for concern. Our team recommends taking this to your dealership to help identify what might be causing this. We'd like to serve as a layer of support between you and them throughout this process to ensure it gets addressed. Please fill out our support form here https://s.chevy.com/support-request  when you can so a member of our team can follow up with next steps.