Re:Is it the gear or syringe?
Maybe the sponk on your bum cheeks is causing a bockage?
Try showering pre jab.
Just kidding... some oils can affect the rubber movey part in the barrel... although i've never encountered any myself. Bmc.s tip was good... warm the vials in hand hot water before you draw, make sure you wipe them off and switch needles etc before you draw/jab and so on though....