I have the same thing happen. I assume it’s because the vials are kept cold so the liquid volume shrinks and when I insert the needle, it draws a small amount of air into it. Probably also why sometimes the needle drips a little as it warms up.
This doesn’t happen all the time for me. Oddly of the three pens I am running right now, only one is doing this.
Hey,
Thanks for the reply. Yes also the dripping issue is relatable - i didn't mention it in my initial post. I'll try next week filling some pens with "cold" vials - to see what'
s what. I've also ordered a new batch of vials from a more allegedly more reputable manufacturer.
Thanks,