Project 245775034 doesn't render correctly

[apple502j]

Expected Behavior

When jumped, the platforms should render correctly.

Actual Behavior

In 2.0, it works.
In 3.0, some parts are hidden.

Steps to Reproduce

Open 245775034:
https://scratch.mit.edu/projects/245775034/
https://llk.github.io/scratch-gui/develop/#245775034

Operating System and Browser

Windows 7 HomePremium 64bit SP1
Firefox 62

[thisandagain]

/cc @ktbee @kchadha @cwillisf