What flavors are you vaping?
After a lot of trial and error, I've come to find out that some flavors trigger very, very painful acid reflux for me. Especially any tart fruit flavors. Which is a shame, as I really enjoy those kinds of flavors, but it isn't worth the pain. I think that the culprit is malic acid, which is a flavoring additive used for tartness. Some vendors add it, but mostly it is already contained in the flavorings vendors use, so it's usually not possible to get a flavor without it if it's already in the flavoring. It has no effect on me in food, so there must be something specific to vaping it that causes the problem.
Fruit is the worst, but I also get it a bit from coffee and cinnamon/spice flavors. Now I only vape tobacco, vanilla, and some dessert flavors without fruit. I've never tried menthol, assuming that it would be very bad for reflux, but I can't say for sure, other than I'm not willing to risk it...