During development, when trying to save an Interactive Grid on either a public page, or when the application has no authentication scheme, you get this error (seen in Apex 19.1):
1 error has occurred
Ajax call returned server error ORA-20987: APEX - An internal error has occurred while processing the Interactive Grid request.
- Not authenticated. for .
An internal error has occurred while processing the Interactive Grid request.
Apparently this is a known bug (Oracle bug #25177537). For more info and a workaround take a look here: https://www.databaseusers.com/article/5990721/APEX+5.1+Cannot+Save+a+non-editable+Interactive+Grid+when+page+is+public