My first guess would be either PG or even diacetyl, but it's the same
juice and only happens occasionally. I have one
juice that bothers my throat and I believe it's PG and diacetyl (tastes like butterscotch even though it's supposed to be vanilla/pecan) Maybe actually wicking too saturated... like you are drinking the
juice. Can you try the same juice in different device? Or just try same device with different juice. Others here know more about building. What VG/PG ratio and what flavor?