I'm no expert in DMS, like you sometimes I think I can taste/smell it and sometimes not so much. There are a small number of recognised genetic differences in perception of flavour/aroma molecules and although DMS isn't one I've seen described, I do wonder if it is one of those that has variable perception.
F2 yeast FWIW is good to have around to sort out off flavours and speed up maturation. It adds on several weeks to conditioning but I think of it as a 'repair' yeast. The Fermentis guidance only uses a tiny amount from the sachet so I keep a sachet on hand in the fridge to add a bit if needed.
SafAle™ F-2