Transmission / TC issue

I'm a new T4R owner with a question for the community about the 5-auto transmission. First, I provide the back story...

The wife and I purchased a 2017 T4R 4x4 SR5 with around 60k miles on the clock from a dealer. We did not purchase an extended warranty, but a 90-day comprehensive warranty came as part of the purchase. It wasn't long after bringing it home did we begin to experience an intermittent 3-4 second delay when shifting from reverse to drive. It would just hang in neutral until you gave it some gas, then jerk forward. After a couple months of living with it, we brought the vehicle back to the dealer to have it looked into. They took it to a Toyota dealership for them to troubleshoot the problem, where it was recommended that the transmission be fully rebuilt.

Almost a month later, we finally get the vehicle back. We brought it home, and within a couple days, the problem returned. Off back to the dealer we went, and back went the T4R to the shop. Several days later, we pick the vehicle back up. Finally, the problem from shifting from reverse to park had been resolved.

However, I am now experiencing what feels like a hard shift under deceleration. I've narrowed it down to be between 5th and 4th gear, and I'm thinking it might be associated with the torque converter unlocking. I also don't experience the issue when running in 4th gear sequential mode.

I don't recall this occurring before all this work was done to fix the initial problem, and it doesn't feel normal. Before I go back a third time and complain, I wanted to bring my situation to a group of experienced T4R owners and see if this has happened to anyone else, or if perhaps somebody with some familiarity with this transmission could provide some insight. I did a forum search, and I'm leaning towards a developing TC issue, but I'm not sure if I'm on the right track.