So when I purchased my 2010 Jk it had 5,000 miles on it. After the first day it popped out of first gear, which then became so random, that I just stopped using first gear. Then I put 35s on and needed to use first more often at stoplights, so a cure was needed. I used a leather outer boot first, which I then modified by opening the upper section up to allow more freedom. It helped but didn't cure. I then cut the lower rubber boot, in hopes of releasing more tension. All that did was create a heat pump into the Jeep. I quickly replaced the rubber boot and it seemed better than the original boot but still occasionally popped. In an unrelated fix, I was replacing my factory crossmember with a JCR crossmember. When I put everything back together, first gear was very smooth, but reverse was popping out of gear. I decided that alignment could be the solution, so I loosened the nuts that hold the transmission mount to the crossmember and then parked on a hill to let gravity move the transmission slightly, then tightened the nuts while it was still parked on the hill. So far this has been the longest fix and it was free. So I would suggest anyone with popping out of gear problems try the same thing.
https://youtu.be/gts9eV9oKr8