oldermodelguy
My suggestion then is to coat the mating surface of the nozzle tip to body with a film of bees wax or lip balm and assemble as usual. Also be sure your paint is thinned enough. Any threaded pieces do well with lip balm as both sealer and lube as well. I have a Paasche VL that likes to blow bubbles out the nozzle cap and that's how I seal the threads to it. Also a film of lip balm on the tips mating surface helps it not stick to the body on disassembly. It's just a good general tool and practice I feel.
When my Badger 200 was sputtering and needed a new teflon ring for the head assembly I got by with bees wax on the old ring till the new one came in. It sprayed fine that way. In fact I tried that first to confirm I needed to order the new ring. It was my test and it worked. I see on youtube where guys use gobs of the srtuff to tune up the chinese knock offs, you don't need gobs of it though.
Really good recommendations from OMG, I have used the 105 model for several years, with careful use and thorough cleaning practices they will last for many years.
A friend loaned me his Sotar to try, at first attempt there was severe bubbling in the cup. Looking close I found a split in the nozzle, I used a bit of bees wax which made a big improvement, just not a full fix, the new part fixed it. I lean toward the 41-003 nozzle being your issue.
If that is not the problem then perhaps the next forward part, 51-071, is not sealing well at the A/B body threads. I've heard that the O ring between the body and that part is not needed, but I use it anyway. You could try some bees wax on those body threads to see if that helps.
How about a good long soak of those three forward parts in some lacquer thinner or acetone, then a gentle wiping to remove residue. I use Badger's "Regdab" lube on all threaded parts, but a vegetable or mineral oil should be OK as well. Worth a trial.
I rebuild A/B's for a large club membership and have a big assortment of new parts, if you want I'll fix and tune your 105 to new condition at zero cost to you, all you'll be out is insured postage. Just PM me for address both ways, if interested.
Patrick