My 2014 XJ has a jammed lock because a towel going into it upon the last closing. Motor works and still wants to try to open the lock, but starts to open but can't. Went to dealer and tried to use push down method while pressing the button and or fob. Activates motor and then stops from the resistance to open. Looked at a video on removing the back seat. When back seat is removed the trunk cannot be accessed due to a metal barrier to the trunk. Doesn't look like that barrier can be removed. Additionally, the trunk is full with my inflatable sailing dinghy that I was transporting home. Hoping someone out there has a fix. The dealer had no real good suggestions.

 

Not really as I was going to suggest pushing down on the deck lid as you have been doing.
Any chance you can tear the towel in small pieces and try to remove as much of it as you can?

Note in this thread the dealer used 4 people to push the lid down! Maybe use a bit more force? I hate to suggest things like this but??
Open Trunk

Be sure and read that entire thread as another suggestion was going thru the rear license plate!
Also note a suggestion to go from the bottom thru the spare wheel well.
If you get it try to post back to help the rest of us out?
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You have happened upon my worst nightmare. There are stories of the trunk/ boot being opened with a forklift.

Good luck.