I know of instances where an engineer has been disciplined for causing a delay to an aircraft - because he tried to fix a reported defect - when the aircraft could have dispatched on time IAW the MEL!
bizdev
Smack on!
Usually the part of fixing a snag which takes most time is the troubleshooting process.
E.g. in this case troubleshooting could have taken easily several hours, while actually replacing the relay would be a matter of minutes.
And, on the other hand, the troubleshooting process reveals that there is no serious fault in the background and that it was all about an easily deferred problem, the engineer will be disciplined for unnecessarily grounding the aircraft.