I don't know specifically about your symptoms, but one thing it could be is the carbonation.
All draught Guinness (including Guinness Draught cans) is not carbonated with just CO2, but with nitrogen and CO2 in a 70-30% (thereabouts) mix.
Additionally, when pouring a typically carbonated beer incorrectly (or not pouring it into a glass), a larger amount of CO2 remains in solution, leading to gastro bloat that can feel more uncomfortable than one would expect. You can experience bad pours even at bars, depending on who's behind the tap.
Lagers will have higher carbonation levels than most stouts, so that could be a factor.
All draught Guinness (including Guinness Draught cans) is not carbonated with just CO2, but with nitrogen and CO2 in a 70-30% (thereabouts) mix.
Additionally, when pouring a typically carbonated beer incorrectly (or not pouring it into a glass), a larger amount of CO2 remains in solution, leading to gastro bloat that can feel more uncomfortable than one would expect. You can experience bad pours even at bars, depending on who's behind the tap.
Lagers will have higher carbonation levels than most stouts, so that could be a factor.