I noticed the blue rectangle (which indicates the visible area) can extend beyond the limits (red area) to eventually the part that displays the game itself:
(for the record, this also happens in feos's encode roughly 10 minutes in)
Not sure if that can be fixed, though, as this was with the most recent version of the script.
EDIT: Well isn't that fan-flipping-tastic. I now have BizHawk crash at complete random when trying to dump with the map script, resulting in the AVI dump being invalid. If this continues, I have two choices: Either I publish without an alternate encode with the map script, or I outright drop it.
BTW, have I mentioned the Lua script makes the emulator run at
15 FPS? (okay, that's not fmp's fault)
EDIT 2: Sorry, but I'm dropping it (until I can somehow get a full dump with the map script without the emulator crashing, and I have no idea what's causing the crash in the first place). Maybe someone else will have better luck.