A833 2nd gear issue

If I'm in second gear and I let off the throttle and an not holding the shifter back the trans will pop into neutral.
This is the only gear that does this. The shift from first to second has a different feel to it compared to the shifting of all the other gears. Kind of hard to put language to it, A little tighter or stiffer maybe? Fluid was changed to a GL4 designed for yellow metals.
Your thoughts????????????
Thanks Marty..........C 55.jpg
Author: FJ5 1970 440