If you are experiencing difficulty adjusting the seat of your ELF, then there may be debris and/or deformities in the rails beneath your seat in which the seat slides.
To address this, first wash the rails thoroughly with warm, soapy water. This should clean debris from the rails themselves as well as clean the parts of the seat that slide in the rails.
Once this is done, then check the rails for gouges, or places where the metal has become misshapen. These may impede the smooth travel of the seat and continuing to slide the seat across such deformities in the rails may further damage the seat, making the seat even harder to slide in the future. If gouges are identified, let us know so that we can replace your rails if they are under warranty.
After cleaning the rails and checking them for gouges, try to slide the seat. If the seat now slides easily, then you are done repairing your seat. If the seat is not yet back to proper working order, then lubricate the rails and the part of the seat that interacts with the rails with a teflon lubricant, wax, lemon Pledge, grease, or oil. These will make sliding easier for contacting surfaces; however, they may also trap dirt and debris in the future and as such avoid these unless absolutely necessary.