SAML Identity Provider Mapper is not editable after upgrade to 19.0.1

We have migrate from 16 to 19.
After the upgrade I wanted to take a look at the SAML Identity Provider mapper settings.
No matter which mapper I click on, I get the following error message:

undefined" is not valid JSON.

All other settings are displayed correctly.

Is a bug?

Has anyone had similar experiences?

Thanks

Alex