glowStack() causes executing stack to hide until glow is removed, on iOS/Android

Expected Behavior

The executing script should have a yellow outline.

Actual Behavior

The executing script disappears.

Steps to Reproduce

We have observed this behavior on iOS and Android for scripts small and large, but in my reproducible case here, this behavior occurs for a very large script in the iOS simulator.

1. Open the vertical playground in iOS simulator (I've tried iOS 9.3 and iOS 10.0. I believe it also repros on iOS 10.3. Perhaps also iOS 11).
2. Paste this xml in the text box for importing:
   xml_for_long_script.txt
3. Import the script by tapping "Import from XML"
4. Tap the green flag block, which is the first block of the long script
5. Tap "Stack glow last clicked block" button

Note: If you remove the last block at the very bottom of the stack and then repeat steps 4 and 5, the script will not disappear, but notice that the glow outside is not yellow but instead is the color of the blocks it surrounds (as you can see if you page down through the stack).

Operating System and Browser

Xcode iOS simulator 9.3 and 10.0 on macOS 10.11.6

Start by reproducing the issue in the vertical playground using the linked large XML, then trace glowStack() from the “Stack glow last clicked block” button. Compare the executing stack before and after applying the glow on the iOS simulator and Android. Done means the full script remains visible and the executing stack has a yellow outline.