Standalone QWebEngine application shows corrupted pages and HTML source code (Ubuntu + 5.9.4 only)

Background

I can create a standalone QWebEngine application that compiles and behaves like a regular web browser when linked against QT 5.9.2.  I'm able to create a standalone image for CentOS 7 that works on other CentOS 7 machines (without QT 5.9.2's development tools installed) and I can also do the same for Ubuntu based systems.  I've been using linuxdeployqt to create the standalone image.

I've attempted to create a standalone QWebEngine application using the same setup with QT 5.9.4 instead and here's what I've found.  In CentOS 7, there's no difference.  In Ubuntu 14 and Ubuntu 16, however, the web pages that appear are malformatted / corrupted - line break HTML tags appear to be ignored, for example.  The source code for the page is also visible in black text.

If I run the Ubuntu 14 application on the original dev machine (one that has QT 5.9.4 installed to /opt/Qt/5.9.4/gcc_64), then it works.  On that same machine if I rename that directory, the pages appear corrupted again.  I've looked for references to this path in the QT libraries, but all I've found is qt_prfxpath in libQtCore.so.5.

Summary

• Standalone QWebEngine app + QT 5.9.2 is for both CentOS 7 and Ubuntu.
• Standalone QWebEngine app + CentOS 7 is OK for both QT 5.9.2 and 5.9.4.
• Standalone QWebEngine app breaks on systems with Ubuntu + QT 5.9.4 when the QT dev kit is not present.

Any thoughts on...

• why this occurs in Ubuntu, but not in CentOS?
• why this occurs in 5.9.4 but not in 5.9.2?

Thanks in advance.