I have a job with anywhere from 500-1000 sql tasks where the sql task is using a sql warehouse instance and running a sql script stored in a warehouse path like /Workspace/folder/file.sql. The sql task will fail with the error:

Run failed with error message 
Failed to fetch SQL file. Please make sure that a SQL file exists at '/Workspace/<path to file>'

The file exists (I know because I click on the link in the job task and it opens the file) and executing a "repair run" usually succeeds.