You’re not doing anything wrong. Other users are having the same issues with Grey on the Form 3, take a look at the misshapen circular openings in this post:
Formlabs has improved the results for this resin since the Form 3 was released, but they still have a little ways to go.
In the meantime, I’m certain if you’re able to print this in Black v4 resin you’ll get better results. Also make sure you’re using the latest Preform and firmware.