you are getting a shot of extra fuel during pitstop but your engine isn't stable enough to handle it without stalling out.. When the tank lid closes a extra shot of fuel enters the lines and is drowning the glowplug and stalling the engine out...All tanks will do this. issue is the engine can't burn off the extra fuel and recover.. As I say the signs of water in the fuel can be subtle and will start showing at places like pitstops where the engine is most vulnerable to flameouts..... But yes....obviously if your too rich or your plug too cold these issues will happen....same if the engine is starting to lose compression, or has a damaged bearing.....