No one seems to have noticed your question so I'll give it whirl. Not a 717 person at all however some things tend to be common.
Most large aircraft have their controls surfaces designed so that they can be made to operate independently, but are normally linked so that they operate together. If something was to interfer with the mechanism of one surface to jam or restrict movement then its mate can still be made to work. The aircraft would have reduced handling qualities but still be controllable.
There needs to be some means of warning the crew if those mated surface are not acting in unison eg the same amount of movement, all actuators functioning etc.
Don't know about the B717 specifically since I don't know anything about its design & systems. It might be common in the B717 due to some design quirk eg on the ground before systems are powered up or a certain speed is reached by which the warning must cease, or it might ground the a/c until fixed.
Hope that helps?