As Rob says, the fact that two machines exhibit the same problem can be useful. Questions:
- Are you using Windows 10 on these machines?
- If yes, have you performed clean installations, or did you update from Windows 8.1?
- Same computer brand? Models?
- Are both machines using the same video cards? Which ones?
- The same antivirus application? Which ones?
- Some utility software running in the background, such as an automatic backup utility, registry cleaner, or similar application?
As I've said multiple times, I cannot reproduce these problems on any of our machines. An 80% of the time is definitely a game stopper, so I fully understand your frustration. Let's see if we can find something that can help us here.
You could perform a clean Windows 10 installation, that is, install the operating system from scratch, including a complete hard disk reformat. With a pristine Windows installation, install PixInsight *without* any other software---including your favorite antivirus; you can visit our website safely without it---and see what happens.
The next version of the PixInsight Core application uses Qt 5.6, instead of Qt 5.5.1 used by current 1.8.4 versions. This might solve these problems, in case they are being caused by video driver conflicts (as I suspect), because the new Qt is supposedly more robust to these issues. The next version also drops QtWebKit completely in favor of QtWebView (Chrome-based) for documentation contents, which is also more robust. This might also resolve some potential conflicts in some rare cases.
Sorry for not having something more substantial to say for now.