Need help with multiple C4 problems

I recently bought a used C4 for my sons Capri. The transmission reportedly had about 10,000 miles since a rebuild, and a B&M shift kit installed. We put it in the car with a 2800 TCI converter. The problems are listed below in sequence:

1. All gears worked well except it had no 3rd gear.
2. Car sat a week and when we drove it aqain all gears worked well.
3. Drove it the next day and it had no 3rd gear again and it began loading up in 1st and 2nd gear like the transmission was locking up.
4. Pulled valve body to look for trash etc. and found that it was assembled with no separator plate gasket.
5. There was not debri or clutch material in pan.
5. Reassembled with Transgo shift kit including gasket.
6 Adjusted bands per instruction, which was "snug with a short wrench" and the back off 1 1/2 turns on the front and 2 turns on the rear.
7. Test drove and had same symptoms as 3 above.

What would cause it to not have 3rd one day then have a strong 3rd a week later, then back to having no 3rd again? Also what would cause the loading up in 1st and 2nd?
I am not sure whether the filler tube and dipstick are correct for the transmission. Where should the fluid level be in relation to the top of the pan?

Thanks,
James