hey i was just curious if this ever happened to anyone. sometimes when i do my shot, i always aspirate, and i get air bubbles, then ill inject, and after i inject sometimes a little bit of blood enters into the syringe, like back pressure forces blood into the needle. and i cant figure out why this happens if i aspirate and dont get blood. could it be just passing through a blood vessel, but i dont understand why blood would force its way back up into the syringe. any input is appreciated thanks