Hi @hmebq_au - It looks like a memory issue, but we would need more information to help.
Could you share the Power Query function that you created to read and transform the files?
Are you reading the file/s from SharePoint Library?
How complex is the JSON? How big? How many JSON files?
You may need to consider separating Power Query from PBIX by using a Dataflow. Dataflow can act as stepping stone in an Extract Transform and Load. One dataflow to read or extract the file from SharePoint. Then another Dataflow to do the transformations. Then load to PBIX file.