Service brakes won't dump pressure?

So I just had my air manifold replaced, and now a few hundred miles later I've got some weirdness going on:

The service brake pressure won't go down. Emergency brakes release, air builds just fine, but if I step on the brake pedal at all, the "real-time" pressure gauge just goes up and doesn't drop back down. And obviously brakes keep holding the wheels.

An even weirder thing: the only configuration it works normally is if I have the emergency red line attached to the trailer, but NOT the blue service line. Then, with both emergency brakes released, I can run the truck on bobtail brakes only, and the pressure drops just fine. That's how I managed to limp two miles to the nearest truck stop...

What the heck is going on? Any advice from air brake detectives out there?

 

This is a '14 Cascadia. The air manifold was replaced (the plastic bit on the firewall where all the different air lines go in and out)

As far as the lines being wrong- unfortunately I don't know very much about the air system. Never really had a problem with that side of the truck until now. I guess today I learn. Any place I should look first?

The weird thing is, it got me from LA to middle of Arizona before this started happening...

 

It was both. I think it was just ice in the lines, because of going from wet rainy LA right into freezing cold Flagstaff. Anyway, I'm at a shop now, might as well get it checked out.

 

Well, the brakes started working fine after I dumped air from tanks a couple of times and weather warmed up. Must have been ice in the lines doing some really weird stuff. Oh well, live and learn. That will teach me to always dump air tanks before going from warm places to super cold ones suddenly.

Now I got another problem - trolley valve doesn't work. Just shoots air into the cab near the feet. Remains to be seen if it's continuation of the ice problem, or mistake from the air manifold replacement.