From all the research I’ve done, it is literally a SSRS/SQL Limitation, if you google the 8060 you will find lots of blogs, hate speech about it.
But what you could do is modify your RDD and exclude Labels and Columns you really don’t need. If you click on each table and go through the Exclusion Tab, there are alot of things you prob don’t need… Especially if you added more tables to it, you probably aren’t using the Labels anyways like Epicor does out-of-the-box, you can probably Exclude all of them (on added tables).
Etc…