A vertical stretch? It can happen if you switch to 240p when aspect ratio index is set to 'custom' and the values set are not automatically decreased to safer limits, but it really isn't necessary to do because enabling integer scale and selecting 'custom ratio' will immediately fix it, or by using a different ar index.It displays it in a wonky stretch fashion on my CRT
You could also try enabling 'auto-switch res', it should automatically set everything for you. It's intended for games that switch resolution in-game, but it can be applied in this case.