Ideally, it should be playable on the current version. I'm getting the exact same error on my end, too, and I think I might know why. If my theory is correct, then by complete coincidence the very first Flowgraph node—out of several hundred—is the culprit. Lemme make sure I can fix this, then I'll come back with a write-up on what happened, in case that could prove useful to someone. EDIT: Okay, got it. Check the spoiler below, in the event you're developing Flowgraph and hitting the same brick wall. Spoiler: Issue Description and Fix So, the culprit was the 'Fade to Black' node, which, contrary to its name, no longer actually fades to black (it now fades to the loading screen). The Hawk fades during resets, walking mode transitions, and in between its chapters, to provide a more polished experience. Now, the 'Fade to Black' node has multiple output pins, which allow the flow to move through the node into other nodes, depending on the conditions. One of those output pins (finished? I can't recall) only allows the following nodes to be activated if the screen has fully faded. The issue is that missions now automatically activate a fade in and of themselves, independent of what the Flowgraph does. And for some reason, fading to the loading screen while the loading screen is already present won't trigger the output pin in the Fade to Black node. I'm not sure why, and most likely all of this means that the first fade nodes are vestigial anyway, but my internal copy now has this patched, so that flow throughout the first state doesn't need to wait.
I uploaded it over the weekend. I was hoping that it would be approved today, but no dice. At any rate, I've updated the forum copy up in the first post, so if you don't wanna wait a few hours/days, you can grab the new build from there.