N8-70 XT/Screen PT-R8800 III Exposure head problem

[Tillmatic]

Hello

we have a problem with a Screen PT -R 8800 III. CTP was delivered to customer. Was working fine till dismantling. Now the following error appears:
Exposure head error. If you press details it says: Error E6EF4 A command was sent to exposure head. But no answer was returned from the exposure head (Echo-back was not returned).
Anyone had this fault before?
Thanks for help.

 

[prepressrx]

Something must have just come lose, so I would reseat every cable attached to the laser CPU.