It could be several issues for loosing pressure the the front clutch pack.
I would pull the valve body out and use compressed air to check for leakage to the front clutch drum.
If that checks out, separate the valve body and inspect the fluid circuit paths for cracks or breaks in the walls.
I had a crack in my valve body wall that had the same symptoms, but that was really unusual.

my thinking is likely pressure loss to the front drum?
ff the trans ran real hot, likely the lip seals in the drums need to be replaced