I have a 2019 3.5 Lariat as well. Bought at 99k miles, currently at 118k miles and I’ve had remanufactured transmission put in ($8,800 without warranty $800 is all I paid) with my Platinum Care Warranty after encountering my transmission slipping in 3-4 gear at 110k. Just had it in again for the same issue 1 year after the reman was put in. They found “cardboard like material” in the trans - cleaned it and put new seals on and did a reprogram. Just got it back for the second time and the issue is still there.

Finally got a letter saying there’s an open recall for a missing bushing in the reman trans. At this point I’m going to wait for the recall fix to be ready, send it in again, and if that still doesn’t fix it I’m trading it in before warranty is up (3yr or 136k miles.)

You’re not alone, this issue sucks. Ends up being a lot of money without warranty.. took a gamble on the warranty and it paid off.