Switch back and forth between two pages timing inconsistent

[chrisgarrity]

Create two pages with different backgrounds (helps with observation).
On each simple script -when greenflag switch to other page.
There are pauses switching pages, but not predictable. The pauses seem to get more inconsistent the longer it runs.

---

Moved from LLK/scratchjr-private#221
/cc @chrisgarrity

[deepankarmalhan]

Figure out architecture of this in rework, put in the product backlog.