Hello,
Car: 2001 CL coupe V6 5 speed automatic

The Short:
Car has 500 miles on newly rebuilt transmission. When you stop at a red light and start to go again it is in neutral and only revs no power to the ground until you slap the automatic into sport mode and drop it down to 1st then it takes off like expected.

The Long:
I bought a 2001 CL 150,XXXmiles with a bad transmission. Pulled it out and exchanged it with a newly rebuilt one from a trusted source, installed it and the car drove fine for about 500 miles, slightly rough shifts from 1st to second but from my experience with Honda's that's normal. Now it started a new problem! when I come to a stop most but not all of the time it will "stick" in neutral and only rev until your move the shifter manualy down into 1st at the very bottom of the shift pattern then it will take off like normal, you can push it straight back up into D5 and drive like normal until you stop and it starts all over again. experimenting with not actually stopping but letting off the gas and allowing the car to coast to a speed of 5mph then attempting to get back on the gas cause the same issues it just revs like it is in neutral and once I sport/manually shift down to 1st or sometimes 2nd it catches and you can drive as normal. I have checked the transmission fluid and it seems to have the correct amount but I am not 100% clear on which dipstick markings mean what for the automatic. Fluid also semed to have some small micro bubbles in it, not frothy but not totally clean like I would expect brake fluid to be.
WHAT IS GOING ON THIS IS A NEW TRANSMISSION! I am starting to freak I really don't want to have to pull this thing again!

Thanks in advance for any insight!