Thanks for the replies guys. To be honest, I really don't know what the problem was but must have been something to do with the pre made coils. When I first got the OBS Engine, I fitted those coils and snipped the leads. But my Sigelei mod couldn't do that low resistance of under .2 ohms so I removed them and built my own coils. Now that I have the Wismec I installed those coils again. The leads were obviously already snipped but there was enough to tighten down.
Thanks for that video dom qp. I only buy and use top airflow RTAs now and so far my OBS has never leaked so hopefully I won't have to experience liquid leaking through the 510 into the batteries. That's pretty shocking. Or maybe the reviewer had a faulty one.
Anyway, I've built a dual coil SS 317L and everything seems fine now. *shrug*