Has anyone had this happen,

I back up from burn out on last pass with pro brake and no delay and after I let go button it should neutral out but stayed in reverse for a sec or 2 then finally neutral out like should.

Cleaned carb out and went to put in 1st gear and did same and it took a sec or 2 to engage into 1st gear.

Ended up being 40 that round and losing so went to load up and I back car in trailer and the same prosses happened again as backing it in and then putting it in 1st to move up. I tried it 4 times and happened every time.

Took it home for 30 min ride and went to pull outa trailer and all worked as should. The 1st gear I woulda thought pump pressure and the reverse issue stuck selinoid. But very odd both them happen at same time. Is there anywhere else I’d look or could be. Trans has 16 passes and was flawless every lap with new converter till that last pass rd4 on 2nd day. I did dbl the car that day (I never do) and lost one entry in 3rd and wasn’t trans issue just lost with 11 pack. But very next pass in 4th this happens

Id pull solenoid and piston and clean everything to make sure dirt isn't hanging it up. Get trans hot again and see if it works.

Dumb question - trans button was not sticking on was it?

Beyond that I would be dropping the pan to see what it looks like in there.

Been getting alot help from will holler enterprise and told me where to look and damm he was right. New trans and new convertor had stuff in trans that got to selinoid on valve body and the external one. Got all broke free and see what happens next week. I highly recommend his service on converters and a lot other items u can get like I off street but go threw him and u get cheaper and he make it a purpose to set up or get how he thinks. And very responsive and way more help then he needed to be

Sounds like piston is sticking in the valve body

Most of the time metal like that comes from the cooler, after a previous transmission failure. Might be wise to invest in a new cooler, or go to a transmission shop and see if they can "hot flush" your cooler.

^^^^ This. I went 9 rds and put the car away for the day. Next day start and warm in place. Called to lanes and wouldn’t back up. No clicking from the TB solenoid and thought it was bad. Turned out the piston is stuck in the valve body (won’t move) and the trans, converter and stacked plate cooler had very fine metal in the fluid. Tried flushing the stack plate cooler and ended up purchasing a tube type cooler for replacement. Sending the cooler to a friends transmission shop to see if he can get it clean on his flushing machine.

Get a can or 2 of Kooler Kleen, made by Lube Gard.
Most parts stores carry it. Spray can that has high pressure solvent and will blast your cooler and lines pretty well. A bit pricey, (about $15 last time I bought it at Advance). But a lot less costly than a wasted race entry.