the glass I meant is the end of the glass injector, the side with the GonG fitting. there it had a bit of a lip inwards, so that the metal heater couldn't get past this point, meaning the thicker part of the heater-part you insert into the glass was blocking the 2 airholes in the glass injector. I can's take pics right now, maybe tomorrow. and I tried, definitely not a really thight fit, it was no fit.
at least I know it works now, and it definitely works well. I think I'm first going to contact vaposhop, since they were the ones who provided the glass part, maybe they got a bad batch or something. I also noticed it doesn't have the herborizerlogo in it, which the pic on their site does have. but that's for later, I hate contact with customer services, and I have a slight fear that because vaposhop is a bit bigger and has a dutch site, they're going to try to call me instead of simply answering my mail, and I hate calling, and being called even more(my experience with customer service is they think it's good to call to resolve it quickly and leave a good image, but they don't get I'm sending them an email instead of calling them for a reason). and I have other things to do woth my time that I don't dread as much.
but didn't want to wait on that to be able to try it out, hence the broken glass-solution. it's only a 12,50 euro-part anyway, so I don't really care if breaking it would void a refund for it not fitting.
just a temporary fix till I can get the right fitting part.