A "torque setting problem" could mean any number of things. Whereas the advertising party didn't elaborate, then you need only know it's an engine/thrust problem. What it is exactly, isn't known.
A torque setting problem could imply a failed gauge or instrument. It could imply a failed propeller. It could imply a failed governor. It could imply a failed fuel control, linkage, fuel topping governor, fuel pump, or any number of other issues. The pilot may be having trouble setting power because he's experiencing transient power or propeller problems, it could be because he's got low oil. It could be because he can't see the instrument indication. It could be any number of other possibilities.
Apparently the pilot wanted nothing more than your runway, and wasn't seeking additional services such as priority, crash-rescue, or otherwise.
As far as potential complications on landing, that will really depend on what's wrong. No particular chance of anything going "wonky," though if it's truly a power problem then the possibility might exist of a power loss enroute. If it's a propeller problem, the pilot may not have reverse on landing...again, not a particularly big emergency.