Pentaho ERROR: "every derived table must have alias"

Question

I'm working on a platform which uses Pentaho for several analysis. Suddenly, without any updates, all the .saiku executing queries with a connection to a specific mariaDB schema don't work anymore.

Via "manage data sources" I verified that the connection is ok, the data preview works fine, all the data is safe and good. The error in the logs, as the title says, specifies that every derived table must have alias which is weird since I didn't modify any of those and they've been working fine since few days ago. For the record, there's enough resources (both disks and ram) and there's no trace of weird peaks on resource usage. Any chance something similar happened to you? Tell me if I can provide more useful informations and thanks in advance for your help.

D.