The adjusters are new and not broken in.

Operate the seat to the full forward and the new rearward positions several times in order to work the new tightness out of the channels.

The adjuster(s) are lubricated improperly.

Lubricate the adjuster channels using Lubriplate Auto-Lube A* or the equivalent.

Bent or damaged channels cause the adjuster(s) to bind.

Replace the adjuster.

The adjusters are not in parallel alignment with each other.

1. Loosen the floor pan attaching bolts or nuts.
2. Align the adjusters parallel on the floor pan.
3. Retighten the nuts.