I've spoken with the manufacturer. They say the most common reasons
for bubbles is not letting the mixture sit long enough after mixing.
The instructions say to mix it and let it sit at room temperature in
an open container for at least 2 hours up to 4 hours. At that point
you should be able to put it into the syringe and go.
If your environment is humid, you'll need to let the mixture stand
for the full 4 hours.
You may already be doing this but your note doesn't say. If you are
doing this and still getting bubbles, can you please email me your
exact procedure so I can relay that to the manufacturer.
Gesswein Co. Inc.