Sencha App Upgrade breaks all builds: Requirement had no matching files (RootStub)

So, I went to the command line and type in: sencha app upgrade because a previous build told me to and now this happens:

Code:

> sencha app build 
Sencha Cmd v5.0.2.270 
[INF] Processing Build Descriptor : default 
[INF] Loading app json manifest... 
[ERR] C2008: Requirement had no matching files (Ext.app.bind.RootStub) -- X:\projects\ext\packages\sencha-core\src\app\ViewModel.js:348:68 
[ERR]  
[ERR] BUILD FAILED 
[ERR] com.sencha.exceptions.ExBuild: Failed to find any files for X:\projects\ext\packages\sencha-core\src\app\ViewModel.js::ClassRequire::Ext.app.bind.RootStub 
[ERR]  
[ERR] Total time: 2 seconds 
[ERR] The following error occurred while executing this line: 
X:\projects\zzz\.sencha\app\build-impl.xml:376: The following error occurred while executing this line: 
X:\projects\zzz\.sencha\app\init-impl.xml:292: com.sencha.exceptions.ExBuild: Failed to find any files for X:\projects\ext\packages\sencha-core\src\app\ViewModel.js::ClassRequire::Ext.app.bind.RootStub
 

What's a RootStub? Why do I now need it? Why didn't I need it before? Where do I get it? My company pays for this product.

Is there any such thing as a sencha app downgrade?

Sencha App Upgrade breaks all builds: Requirement had no matching files (RootStub)