I couldn't find a better spot to put this, but this may be a similar issue. I've already sent a few requests in to support with no answer.
I'm in the same 'Team Edmund' quest, but I cannot leave Edmund Shipping after giving the Aether Boiler to Edmund. He installs it on his ship and leaves. I have dialog with Irving, then with Julian. Both tell me to go to the business district, but I can't leave! I use the ( possible spoiler ) airship communicator to leave the area, but the quest resets back to installing the fog injector on Edmund's racer.
I already have the homing ballon in my inventory, though Julian tells me to get another one from the crates. I've done all side-quests up until this point, so I'm kinda stuck...
Also, may be related: the whole racing scene is glitchy. The camera pans to various views and I see explotsons/fireworks but all the racers are stuck in place.
Running this on macOS Mojave.