Goodness! I am not the only one having this problem? I may have a solution that may save you from a lot of stress.
I have now found THREE boxes where the syringes had a malfunctioning lure locks! Meaning that if you actually twist the needle it turns but does not actually "lock" as a lure lock is supposed to. Sometimes it acts as though it gets a little tight but it does not actually stop. Sometime it just turns and turns and never locks at all! What this means is that when you push the plunger the medication will not inject because it's not a closed system. You can change the needle, it won't inject. You must change the actual syringe!
This totally stressed me out the first time because I was afraid the medication would solidify but it did not. It stayed viscous. Through quick problem solving I was able to fix it.
Now always have back up syringes and double and triple check my syringes.