Error code on XTL2500

[RF1]

Anyone successfully repair an XTL2500 chassis with error code FL 01-90? I have two chassis displaying this code. Replacing either of these with another chassis with same accessories resolves the problem.

[YouHF]

That's a problem in communication with the head. Check your connections and then try a control head sync.

[RF1]

We already had tried the control head sync. Cables and head are good. Another chassis works fine in that setup.