Shifting problems with second and sixth gears only

1, 3-5 work fine.

I can drive it just fine in sport shift mode while starting on third gear and only going to fifth gear.

Going from first to second or fifth to sixth, the second and sixth gears slip or don't catch not always but mostly to the point I really need to avoid them.

When it slips enough, p2714 code shows up with p0700. That's all the codes.

This code shows up before and after a full TCM replacement and programming. Transmission fluid level is good.

The problem has improved with the new TCM as I can now shutdown the car and start it back up to get it working again or stay in third-fifth gears. As well as previously, it would go into limp home mode until it cooled down enough. Now, with the newT CM TCM and fluid, it keeps going and shifts are fine as long as only third-fifth gears are used, no error code and no limp home mode there.

What would I try next?

Could the new TCM have a problem? Could the programming be not quite right? Its Chevy oem TCM and Chevrolet dealership did the programming.

I will probably schedule an appointment with local dealership to see what they say as well.

Thanks!