cpt and Doc,
The problem Doc refers to is for DECUs with the TU109 software. I think the solution for that is to remove those DECUs and wait for a new software mod.
I encountered a similar problem with a C+ during training. On one particular aircraft on one engine, If I froze a DECU at a relatively high torque setting (70-90%) it was not possible to move the FFCL in the manual track. At a lower torque setting, or even at high torque on the ground it could be moved ok. If I remember our engineers checked for any cable rigging problems or snagging. I think it was only finally resolved by changing the FCU.