Why would elements done with the "Move In" feature freeze and become non-functional in the middle of a scribe, and thus freeze all remaining animation?

That would probably only happen if you are using very large image file sizes, excessive zooming in or out, lots of fonts hogging the memory , improperly prepared SVGs or some other type of problematic settings or elements.

save a copy of the scribe online and tell support the name of it if you want them to look at it.

attach the scribe here if you want other members to look at it

read these articles if you want to solve the problem(s) yourself:
INSTANT ANSWER: crashing-and-freezing-videoscribe-free-pro-and-edu

 COMMUNITY TIPS to avoid crashes, freezes, failure to render or erratic behavior (2015)

-Mike (videoscribe user)