Maybe "filler" isn't the right word, but the middle of Act II is a somewhat long span of nothing musically remarkable. If you look at the "favorite song" poll on this forum, there's a big gap here, too, so it's not just me.
At this point, you've been listening to the same style of rock opera music for an hour and a half. It would have been the perfect opportunity to throw in a curve ball and make Machine Chatter into a full-length song, maybe throw in some ambient guitar for some texture, etc. I feel like I am just starting to get into the groove when it ends abruptly.