Sounds like a problem with the positive pin in the mod. Have you got a different mod you could try?
Try pulling the center pin up some more.
tried it mate, doesnt make any difference. I'm thinking maybe the insulator on the 510 pin on the eleaf might be buggered
Don't own an istick but seen plenty of people having issues with it similar to this.
They fixed it by raising the 510 pin on the mod a little. Carefully lever it up with a paper clip or something.
I do own a magma clone and recall the 510 threads/pin are longer than most atties so by screwing it onto the istick you may have depressed the pin too far for other atties.
Not 100% sure about the magma issue though, does the 510 pin protrude from the threads much?
Sounds like what happened tp my mpv2. Put magma on it and it looks like it split the positive pin insulator on the mpv