My extension cabinet is equipped with a Fiber card and main cabinet with a Fiber D/Board. The distance between the cabinets is 620m and covered using a single mode fiber pair. quite randomly my analog card at the extension cabinet disables all the TNs. the only remedy for service restoration is usually to physically remove the entire card and reseat it in the same slot. DISC and ENLC commands do not work. What could be responsible for such behaviours? I have others sites with 10m run extension cabinets that have never had this fault.