Any new data source causes error: "An item with the same key has already been added."

I have an existing PowerBI report with a lot of Sharepoint folder sources. After upgrading to July '25 or Sept. '25 PowerBI versions, anytime i try to add a new data source, blank query, copy/paste a dataset in PowerQuery... they all result in an error message of "An item with the same key has already been added" and the error log appears to show the failed new dataset listed twice as well at the end. My only known fix is reverting back to March 2025 which is the last known working version of PowerBI with this particular report. The report is very complex and re-creating in a blank file with the latest version is not really an option. 

This seems like some kind of bug, but i am not sure how to resolve on my own. I have additional reports made with the latest versions of PowerBI i need to work on and uninstalling and re-installing different versions of PowerBI is not a sustainable solution.