UPDATE - I just spoke with Traeger Support, they were very nice, we went to video chat and I showed her where the grease had leaked. She researched and came back with this; The gasket seal for the grease drawer is NOT REPLACEABLE (fact check, not true). She was ready to replace the drawer and cover, I showed her that it was like new and was not the problem.
She added a 2nd support person and we recorded the video of me pouring a pitcher of water onto the grate drip pan to test the drip system. The water ran swiftly down and out into the drawer, and of course, it didn't leak at all.
I explained that this leak was really only occurring because of my longer cook with heat and a long slow flow of grease. She said to just take pictures next time and we could re-visit the situation. So, the next time I cook anything that will drip a lot, I'll be suspending a larger drip pan below the drawer to catch any leaks.
Last thought, do not open the drip drawer until after the grill is cool. There is a possibility that if you check the drawer while cooking, with any grease flowing, will run onto the top of the drawer at that time. After you close the drawer it will eventually run down the top and drip outside the back of the drawer. My seal looks fine, and my recollection was that I saw the spill, then checked the drawer thinking that it was overflowing, only to find that it was only 1/3 full at most.
Take your pictures and show them to service, my current thought is that the seal should be high a high temperature silicone accordion shaped boot. There should be an engineering retrofit kit made.