The adjusters are new, and not seated.

Operate the seat to the full forward and full rearward positions several times in order to eliminate the tightness from the channels.

The adjuster(s) are improperly lubricated.

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

The adjusters are binding because of bent or damaged channels.

Replace the adjuster. Refer to Front Seat Adjuster Replacement .