95 Ram 2500 Transmission shift question

I have a 1995 RAM 2500 with 80,000 miles on it. When the trans is cold and if it hasn’t been driven in a few days the trans sticks on the 2-3 upshift and will only shift if I lift my foot off the accelerator. If I drive for a long distance that day or If I drive it 4-5 days in a week the transmission 2-3 upshift will come without lifting my foot but will only do so once the vehicle is traveling 52-54 MPH. I was told that there was a TSB or a recall on this problem through a Dodge dealer but that it would possibly cost around $400 to repair. This truck has had this problem from the day I got it from my dad’s estate, It had 54,000 on it then. Is this something that could be related to a shift solenoid or is the transmission going to need a rebuild? Other than the 2-3 upshift sticking it drives normal.

What does the transmission fluid look/smell like?

Tester

Tester - The transmission fluid is cherry, no burnt smell etc. other than the normal smell that ATF+4 has. When the transmission does shift on its own the 2-3 up shift occurs at 46-52 mph.