It may be better to go back to using an MTS or LTS version of Mendix Studio Pro. Mendix 11 is still in beta at the moment, whereas the MTS or LTS versions will be very stable and suitable for production work. These versions don't need React, so the widgets should work.
Change the App Setting at: App Settings > Runtime > Use React Client from 'Yes' to 'Migration mode' or 'No'