Update: If you read through you will find that renaming widgets was the issue.
Up to now I have been working with Dev Edition v1.1 and wanted to try migrating to v1.3. When I ran into trouble, I tried migrating to v1.2 where I did not encounter this error:
My project has 2 custom widgets that I developed, but only one of them fails. A third widget that also fails is simply a copy of the argis-map widget that I renamed and made a few changes in mapbase.tsx to disable all navigation (replacing/enhancing the functionality of the disable zoom scrolling option). All 3 custom widgets worked correctly in v1.3 when I tested them in a new ExB project. Again, I have no problems migrating to v1.2.
I also see errors in the server command window:
Any thoughts regarding this would be appreciated.