you can use one figer on the other side of the plunger to pevent that from happening.
Damn i tried that today.....half ml came in good with no finger for help.......then it stuck again in the middle.....i put the finger to prevent going through directly but nothing!
I pushed with as much pressure as i could (not to cause an injury though) but nothing, so i was too afraid.
I then removed the syringe with a new needle and injected somewhere else.
WHY IS THAT?

should i shake the ampoule the next time? lol, i don't know...
thanks