I was getting errors like "Error: multipleDefine(…)" and "Uncaught Error: declare: base class is not a callable constructor." in the console.
The error
Error: multipleDefine(…) (anonymous function) @ dojo.js:15 (anonymous function) @ dojo.js:15 _9 @ dojo.js:15req.signal ... Error: declare: base class is not a callable constructor. err @ dojo.js:15 _1b3 @ dojo.js:15 (anonymous function) @ widgets.js:2_c8 ...
Cause and solution
This can be caused by various addons in Visual Studio, the simplest way to solve this is to disable the browser link in Visual Studio
If this doesn't solve the issue. Disable the browser link option and restart Visual Studio.