"He who marches out of step hears another drum." ~ Ken Kesey
Even though other's may say I'm wrong IMHO your not going to vac enough water off the screen to go straight to coating if your doing that, water has a way of hiding in crevice's and running down the screen when you least expect it (been there trying to hurry a screen).
Interesting, as they are both 38% solids. I would have guessed that the problem was with much less solids with the LX 680. They don't state the viscocity of the LX-680 to compare, but perhaps that could be an issue.Did you say that you have been successful in the past with the QX-1, same coating, same mesh, same drying?btw, most of us will take exception to your coating method as it is pretty well accepted to end on the squeegee side to force the coat out to the substrate side where it does its job.
I've seen emulsions that were supposed to have the same solids content but be completely different viscosity wise. 38% is low in my opinion and it wouldn't work well with most of our thin thread mesh with big open areas. We had the Ulano Orange do this on one of our 83/71 with a 2/1 coat but when coating it again with Saati PHW Red it didn't happen. I bet the 680 is a lot more runny when pouring it out of the bucket versus the QX-1.