Unintended consequences.
Unfortunately you never know what else is on the circuit when you start pulling and /or resetting breakers without a specific procedure.
One of our crews lost both internal speed cards on each one of their EADI's (B757) in fact each one was red flagged.
In response and quite reasonably they reset the 'Speed Card' CB's on the overhead.
They were very surprised to then see the RAT extend where it stayed for the rest of the flight, naturally as it cannot be retracted once deployed.
Unbeknownst to them or anyone else in flight ops this is how Maintenance performs a RAT test and the circuit is shared with the 'speed card'
It did fix the speed card though..
