Catastrophic failure (Exception from HRESULT: 0x8000FFFF (E_UNEXPECTED )) in UWP app

I would right-click the .xaml file and "Open with..." and select 'Xaml Designer' or 'Xaml Designer with Encoding' and this would bring up the xml text file. If I try to open with 'Automatic Selector' I get the exception popup.

The only thing that was throwing the error was the connected services functions. I could not add or maintain them.

I had to restore my entire code base to resolve the issue. I pulled the last stable build and then reintroduced my changes until I had it stable again.

We have a fairly large WPF code base comprised of VB, XAML and C#. We use a hosted SQL Server database and that is what the connected services were for. I only noticed the problem when I was attempting to add a new table. I should add, we use netTiers to created the classes for the hosted data.

I was not able to determine the exact cause because only a total wipe and reload worked. I do suspect that an MSI project I worked on that used WIX was the culprit. That is because I am the only developer to use those and the only one who experienced this issue.

So a lot of conjecture, I admit, but starting with a clean stable build from another developer solved the issue.