4runner transmission acts like its in neutral after warmed up

Hi all. I could really use some help on this one. It’s weird but reproducible.

I have a 1999 4runner with an automatic transmission.

After the truck is completely warmed up, you can reproduce the problem on demand.

After driving on a highway (anything above about 55mph), and coming to a complete stop (like at the bottom of an off-ramp, or stop sign), the truck acts like it’s in neutral. If I shift into L before stepping on the gas, the car moves forward without incident and I can shift up through the gears to D and be on my way. If I give it any gas BEFORE shifting into low, it shifts VERY hard. There’s no problem if I don’t drive at highway speeds before stopping.

I have a check engine light (P0773) for “shift solenoid E electrical”. So i dropped the pan and checked the resistance (got 8 ohms, cold tranny) as well as hooked it up to 12v to test it and it seemed to work fine. I took it in to the dealer and they said the solenoid is fine. But they got 16ohms, after the tranny was slightly warmed up, They said it was “most likely” an internal mechanical problem and sent me on my way.

I’ve drained the fluid 3 times and changed the filter, with no luck.

Has anyone else experienced this? Any suggestions?

Thanks in advance,