When you go back I would ask if the shop has a mod or apv that you can test the atty on, by the way your describing it, it sounds like the battery is triggering a protection mode because the draw becomes too heavy for your specific battery which for safety concerns on that battery cause it to stop. I'm almost willing to bet that on a 18650 it'll fire like a champ.
Now even then, as far as flower vaping goes it probably won't be a good vape. In my experience every pen style attachment that claims to do both concentrates and flower always, while still being able to smoke, it almost combusts the flower rather then vaping, causing visible blackening of the flowers within the first few hits, and eventually reducing the flower to blackened ash mush by the time it's done. Anyone who vapes properly knows that their is always flower left at the end of a session, even if it darkened a hair and smells like burnt tea.
I've never owned a personal portable vape for flower, but for ease, concealability, and good vape production, I've heard a lot of good things about the Pax .
Hope it helps