What happens when it goes wrong!
In the company I work for we recently had the situation where on a 757 with RB211 engines a damaged EPR sensor rake caused the engine to produce excess thrust.
The commanded EPR and actual (as measured ) EPR values disagreed which left a command arc showing on EICAS and apparently caused the Autothrottle to further command additional thrust.
This situation came about due to the loss of a single pitot type probe head on the EPR sensor rake.
If the engine was being controlled on commanded N1 rather than EPR then the problem would not have arisen.