So as the title says on 2 different occasions the car randomly shut off while driving at around 2.5k rpm.

The revs just went down and the engine turned off but I was able to start it again. Could it be due to a bad alternator? The alternators output voltage drops as low as 13.2V and goes up to 14.2V but its not stable. Could that also be the cause to flickering lights?

Thanks

That is a stable voltage taking into consideration engine revs, current draw from lights, screen heater etc and recharging after a cold start.

 

13.2v would be plausible at traffic lights after having driven a couple of miles.

 

14.2v plausible at higher revs after cold start or with higher current loads.

 

The flickering and shut down sounds like a fracture in the alternator field excitation wire, I believe this happens on the Fabia, someone else hopefully will confirm and explain where to check.