Show the points where movement catches as well as the full track. Local damage may have a different repair option from extensive wear. Photographs help describe the problem but cannot establish that the track, rather than the rollers or frame, is the only cause.
The extent of wear, available parts and access affect the choice. A small repair may be reasonable on an otherwise sound compatible rail. If replacement requires specialist panel handling or rebuilding the threshold, it falls beyond the ordinary task offered here.
Some systems accept a repair insert, while others do not. The insert must suit the profile, roller contact and available clearance. An improvised cover can change the panel height or movement, so compatibility should be established before materials are purchased.
Repair an accepted accessible rail or fit a compatible running insert or replacement section without changing the building envelope. Scope limits: Accessible non-structural running rails only. No threshold waterproofing alterations, drainage-system redesign, structural changes, major glazing or powered operators.