We just upgraded to 9.1.1 and have been facing a lot of issues after it.
We tried republishing the data sources but it didn't resolve any issues.
We observed that if we reduce the amount of data being pulled by shrinking the date range, it resolves a few of the errors.
The error messages that we get are not at all intuitive and we are not able to provide any solutions to our users.
More than 500 users across the organization depend upon reports published in tableau and these errors have been causing a lot of problems to them.
Attached are few of the error messages from the reports.
HI Durgesh, you're right, there isn't much helpful information in these messages. Your best bet is to contact Tableau support.