Could b loadsa things.
Could be boiler running a lot in heating mode in badly ventilated room. Oxygen level drops, pilot light lifts searching for oxygen, flame loses contact with thermocouple and goes out.
Could be dodgy thermocouple.
Cant remember boiler well does it have safety switch in flue or overheat stat through an interupter in thermocouple like Sime atmospherics have.
One of these devices could knock out pilot light.
public room guys lol, but yeh wot spark said , find out when last serviced because me personally id replace the thermo for all the cost and you know yourself replacing the thermocouple means removing the burner so your aswell sticking the hoover in while shes open and clean out injector and check spark etc, then see if problem persists,