904 shifting weird

I've got a used 904 behind my 318.
I got the trans several years ago, it was pulled from running 74 Dart. And that's all I know about its history.
When I got it, I put in new front, rear, and selector shaft seals, a new pan gasket and filter, and filled her up with fresh fluid.

It's been working fine until a couple weeks ago. Seems to shift fine when its cold, but after it warms up good it starts acting weird. Like very delayed 2-3 shift. Its like driving around town, taking off from a light, it will shift perfectly fine one time, and the next time I will get the delayed 2-3 shift. And a couple times is has shifted down abruptly from 3-2 when decelerating.

Checked the fluid when I got home today, fluid is so clean you can hardly see it on the dipstick. But checked it 3 times to make sure. Checked when hot, idling in Park, it looks like the fluid is about 1" above the full mark.
Will too much fluid in the trans make it shift funny or do I have something more serious going on?