"I doubt whether coffee could penetrate the conformal coating of pcb's and the like, unless they are overheated."
Haven't looked at the wiring under the pedestal in a 777, but there are probably canon plug connections under the floor for the thrust lever position-sensing wiring (trying to keep it simple here for beginners). Oil and fuel get into them, so why not coffee?
However (and I'll say this again for those that weren't paying attention earlier)... there are independent circuits/wiring for each thrust lever. The chances of coffee getting into two different plugs at the same time and causing the same type of failure is rarer than...... 777 accidents.
...and hey, don't they have coffee cup holders on BA 777's??? (They do on their 747-400's).
(Edit) After further checking. The thrust lever position resolvers/wiring are mounted at opposite ends of the very wide assembly under the cockpit floor. The resolvers are not separated merely by the width of the thrust lever knobs. In
each resolver, there are two channels (two sets of wiring) which feed the A & B channels in each EEC (fuel control computer on the engine)