Air leak into vial?

I got a vial of UPA Mast Prop, and when I pierce the stopper on the vial with a drawing needle (I use 23g or 25g needles to prevent coring), loads of bubbles fill into the vial. If i ever so slightly move the syringe side to side even more air bubbles rush in and bubble through the oil. By the time I have drawn out my dose there are loads of bubbles sitting in the oil in the vial.

I have never had this happen before with a multidose vial, my assumption is that the rubber stopper is a manufacturing dud and has failed outright?

What is the risk of infection now with this oil seeing as load of ambient air has been entering the vial?

Where does the air leak occur? Between the glass vial and the rubber stopper or through the rubber itself or through the hole created by the needle?

Did you inject air into the vial before withdrawing to prevent a vacuum forming inside the vial?

There is a vacuum created in the vial from when you previously extracted the oil through the needle. So it should be easy to test. No vacuum when piercing the top next time you use it, not air tight.

I figure that if milk can be pasteurised in only 30 seconds at 65C, then it can't be too hard to sterilise the vial again with a bit of heat and alcohol to clean the top.

Funny enough this happened to me earlier with a test cyp vial, loads of bubbles.

This - "through the hole created by the needle"

It appears to be leaking in from where the needle is puncturing the stopper...so in essence the "seal" between the surround rubber and the needle after penetration is not airtight..Like the surrounding rubber is too stiff and not expanding enough against the needles circumference.

Yes my standard protocol is to inject equal volume or or ever so slightly more air into the vial of that which i will be extracting in oil.