Your truck does have a 545rfe.
I'm getting a 3rd to 4th gear buck as well as when I let the truck sit for a while a neutral to reverse or drive la
As for this... Is this only when it sits for a long time(like overnight)? So when you start it in the morning and put it in reverse(or drive) it "oozes" in to gear? If so, it likely has an aftermarket trans filter installed that does not have the anti drain back valve like the mopar filters do. Without this valve, the fluid from the torque converter drains back to the transmission and on cold start there is no fluid in the converter to transfer torque from engine to transmission. So you have to wait a minute for it to refill. I don't know if this would cause your other issue but it might. I'd start by dropping the pan and replacing both filters(there are two) with mopar filters, refill the fluid, and see if it helps one or both of the issues.
Here's a thread I made for regular service:
All this info was explained to me by transengineer, another member on here that is very knowledgeable.