Hi Brian, yeah that will be because of the change in threading model for how scripts are run. In MoI v3 scripts were run in a separate process and used inter-process communication with MoI.exe to retrieve properties and such. That has a fair amount of overhead but it also made it difficult for an errant script to lock up MoI because it could be torn down any time by killing the worker process. In V4 the .js script file for a command is run on the main thread so there's no interprocess communication (same as if in V3 you moved your code over to the .htm file) so a lot less overhead, but it's also easier for it to lock things up if it doesn't behave well like if it just churns away continuously in a loop too much.

- Michael