WEIRD issues with my truck....

My truck is doing some weird ass stuff.... No way to explain it very short. My new built Trans has been flawless for a couple months now.. Saturday I got on the interstate and set the cruise and drove about 40 miles at 70mph. When I got off the interstate and went to take back off, when the truck went to 2-3 shift it just went to neutral. I slowed way down and took back off and it shifted and went on. Threw the P0730 code or whatever it is for Incorrect Gear Ratio. Ever since then, ONLY the first time you take off it does this : start the truck, drop it in drive and feel it engage 1st gear. Then you feel another engagement, like it goes into second while still sitting still with your foot on the brake. You take off, the truck tries to 2-3 shift and goes to neutral for about 5 seconds. If you manually shift it down to 2nd and start back off, it will go to neutral ONE more time when it tries to 2-3. Then throws the incorrect gear code. You can take it back to 1st manually and shift up through the gears, but when you go up to 2nd it doesn't shift, when you go to third it does, then to D it shifts 3-5 like normal then to OD just fine. From there on out, you can leave the truck in D and it will shift itself no problem. BUT; it is taking off in 2nd gear and when it goes 3-5, the converter locks shortly after usually, but now the converter locks AND it shifts to OD at the same time. The truck does this SAME exact pattern every time you turn it off and start it back. My Trans has been 100% flawless and this problem started all at once with no reason or warning. I've tried every tune I have and all canned tunes. Trans does not get hot (168° max) and does not smell burnt. It doesn't physically slip, just goes to neutral when it acts up.

Anybody ever had this issue or know what it could be? The only code I ever get is the incorrect gear ratio.

Bump........?
I had a thought in the shower last night, where I do my best thinking. I remember when assembling the solenoid body, TransGo sent me a billet plug with an o-ring on it to go in place of the plastic dummy sensor in the solenoid body with the updated Low/reverse snap ring. I installed that plug, and remember it being a pain in the ass to get it to stay in there with the little cheesy junk clip that holds it in. Anybody ever had that plug pop out and cause this issue?