Oh hey, there are bugs here. I only fixed the ones that were e-mailed to me. I'll pick at these and see what I can do (people even use this thing?), thanks for some of the detailed bug reports.

(Rather pure luck it was right on the front page or I'd never even have noticed, I actually clicked it thinking it was someone else's AL script and I was curious to look at the code.)
@Xaiko: You can increase the X_OFFSCREEN_SQUARES and Y_OFFSCREEN_SQUARES at the top (instructions are in the script) to make it update as many squares as are needed to keep your event moving offscreen, probably around the ((width of image / 2) + 32) / 32 squares.
@maia: I see what you mean, the reason it's lagging is because the map does some up-front processing when a map loads to lessen the amount it has to do regularly on the map. I'll use this analogy: You want to clean up 5 rooms with a broom. The initial way VX did it was you would get and use and then put away the broom for each room. (You fetch and clean, then put the broom away all 5 times.) The script makes it so instead you simply take the broom out when you start, and put it away when you're done with all 5 rooms. This is similar/identical to many games with loading times; they're doing a lot of up-front processing to set values so that the system doesn't have to calculate them out each time.