It needs better atomization via higher air pressure , thinner mix OR spraying closer to the work to prevent the paint drying in flight before it hits the work .
Keep an eye on the needle tip and make sure paint isn't building up there .
Also, make sure the air around you is clean and not dusty... And clean the model... I've seen this before, apart from what urumomo said, which is good advice, you should make sure everything is nice and clean.
Also 40 psi is a lot, the paint will dry before it hits the model.
FWIW, I've never heard anything good about Vallejo primer. I've heard that masking yanks up paint jobs all the way down to the bare plastic. If it looks like tiny hairs but they aren't, it sounds like either a pressure problem or it isn't thinned enough.
Seriously... if you can get Mr. Surfacer 1000 and thin it with Mr. Leveling Thinner, that is a fantastic primer to use. Or Mr. Base White + leveling thinner if you want to paint a light color or you are working with red plastic or something and wish to paint it a totally different color.
Also, this is probably a conversation more suited for the painting section rather than the SF section.