After upgrading the Enterprise deployment from 10.7.1 to 10.9.1, all the web applications (native) with custom widgets stopped working with the message Cannot read property 'version' of undefined.
Although, there is a topic on Community pointing a workaround, there is no mention about this behavior on documentation. It only says the extensions (widgets) must be redeployed:
"You must also back up extensions for ArcGIS Dashboards or ArcGIS Web AppBuilder. The upgrade will not preserve any extensions you have deployed for these clients. Once your upgrade is complete, you must redeploy your extensions."
Could you please update the documentation and include some notes with the concerns when migrating to a new version of framework? It will be helpfull for the community when doing the migration plan.