Loss of correct torque indication is not that unusual. Fluctuating torque could be anything from gauge or transmitter problems to damage within the engine.
Dispatch without torque indication would be a no go, so a return to major maintenance base would also be a smart move. It seems that the crew decided that it did not warrant shutting the engine down, or that would have probably been added to the report in typically dramatic terms. So, what is hard to imagine?
The problem is, any turn back these days is cause for all sorts of speculation and innuendo. Particularly when the airline concerned is already in the spotlight for its recent accidents.