We do have here cardinal problem... this gun is totally and utterly unsuitable for latex paints! it's nozzle size is 1.4mm, for latex you need at least 1.8mm and preferably 2.4mm, if undiluted even more... any trickery with air flow valve, paint flow (needle) valve or spray pattern will not work, latex particles are long, stringy and clingy - you do need bigger nozzle and that is all...

by the way - it is lovely gun, nice to hold and work with, but it is usable for fine particle paints only, regardless water or solvent based, it is fine gun, but haevy paints based on latex or bitumen will physically just not go through it correctly...

hope this will help you at least a bit, please post your comment how it work for you.

Thinning the paint is always best,but some gun manufacturers dont put on an air cap recommended for latex paint try using an air cap with biggers holes this will allow the paint to flow through better.It could be that the air cap you use now has to small of holes for the paint to flow through.

I dont have so much as a solution as a couple of things you can try to figure out whats going wrong.

make sure your compressor can handle 10.5 CFM @ 50psi
hook up the gun and dry spray it to check for blockages in the air supply
if the air comes through strong and constant, fill the paint hopper with water and spray until empty
if the water comes through constant, add half of the hopper with paint thinned with penetrol or floetrol
if the paint is coming out weak or spotty, make sure the vent cap is open on the paint hopper
if the cap on the hopper doesnt have a vent, try spraying with the cap off or cracked a bit.
if that doesnt work take off the hopper and check the filter for blockages.

i suggest straining all your paint before pouring it into the hopper