On Swiss railways, “unspecified delay” means that no prediction can be made as to when a service will continue its journey or stop at or depart from a later station.
Possible reasons for an “unspecified delay”:
A train has a technical problem at the station or on the route which cannot be resolved within a fixed time frame.
A problem with the infrastructure cannot be resolved within a fixed time frame, causing suspension of service on the line (e.g. broken rail, damage to the catenary).
Natural disasters (e.g. landslide) causing suspension of service on the line.
There is a medical emergency.