well stefan, if we had a complete serial number it might help more.
But....
after looking in the error code list, the 56 code is omitted, it jumps from F55 to F57. Both of these codes deal with the tilt solenoid operation be it either fwd or back tilt operation.


could be possible they installed the wrong controller?
most if not all of thier controllers have software revisions and if it is not the correct one it could cause this error.

if not then doublecheck the connections.
also it may need to be calibrated.
use the GSE tool and check the settings for hydraulic controls, the new controller may be set to the wrong settings. I believe you can use this tool to change the settings to what they should be.