Pens are not my preference because they can still have pressure behind the dose that your tissue is holding back. They work better straight in rather than angled. The fine needles can also bend easily and block inside. I stick with regular syringes where I can watch the plunger move and know exactly what is going in. I draw up a full milliliter, use it until empty, and swap the needle if needed, keeping different compounds separate.
We have used these pens for quite a while across a couple of versions. Lately I have seen one or sometimes two or three drops come out after finishing a shot. I do the injection at about a 45-degree angle, count to ten, then pull the needle out. This never used to happen before, so I wonder if others see it and what might be causing it.