Yep, I’m currently running two machines with num_workers = 0 and 1 to see, but it will take an hour or so before they get around the number of steps it’s been consistently happening at.
Update: Got past 20,000 steps without issue. So it seems likely it is due to multiple readers reading from the same file. Thanks for you help!
Update 2: num_workers = 0 works. num_workers = 1 still results in the same error.