I have faced this issue many times . If in your widget js file has some error code or some code that does not supported by IE, then this error will come.
First need to understand how widgets are working in mendix. You can refer this link https://docs.mendix.com/howto50/creating-a-basic-hello-world-custom-widget
Most of the time, clearing the cache fixes the issue. If not maybe take a look at this post: https://forum.mendix.com/link/questions/10442