HTML5 - Mac - Packaged build does not run

Packaged shipping HTML5-Mac build does does not open in Safari. The user is prompted with a missing shader cache message (see screen cap).

Occurs: with Development and Sipping builds. However, with Development build, the message text is blank (see screen cap)...
DOES NOT OCCUR: on Windows builds in either Chrome or FF

1. Open UE4Editor CL=3135292
2. Create new BP project (used Third Person)
3. Settings:
   • Desktop
   • Max Quality
   • No starter content
4. File > Package Project > Build Configuration > Shipping
5. File > Package Project > HTML5
6. Save package to any desired location
7. Once packaged, Run RunMacHTML5LaunchHelper.command
8. Open Safari enter localhost:8000 into the address bar
9. Select the <YourProjectName>-HTML5-Shipping.html

Result: The global shader cache file ...GLSL_ES2_WebGL.bin is missing (see screen cap) message appears and game does not initialize after closing the message.

no call stack... see screen cap. Why can't I copy the stack text from the browser?