Issue Export Summarized Data & Fields Parameter

Since this morning, users can no longer export "Summarized data" from a matrix visual. The matrix uses three Field Parameters (on Rows, Columns and Values) to let users dynamically choose the fields to cross-tabulate. No changes were made to the report or the semantic model. The following error appears:

"Couldn't create the file. Generating the query for the Export data operation resulted in an error. Verify that the visual contains measures from more than one table, because in that case an error may occur in the data export operation."

Impact: All users of the report are affected. Export "Data with current layout" still works, so the issue is specific to the summarized-data query generation.

Expected: Summarized-data export used to work with this same visual until 11 Sep 2026.

Note: This appears to be a service-side regression in the summarized-data query generation for visuals using Field Parameters with measures from multiple tables.

Are we the only ones with this problem??

Have any of you come across this problem as well?