I had something similar happen with a DVD iso. It would not copy across network, and cpu would skyrocket if I put it on drive another way. For mine it turned out to be the tracker-miner getting hung up on the content indexing. Specifically it was a DVD with a prank menu option. The menu option was “Break my player” which if you chose it would totally lock the DVD player and only fix was unplugging it for a hard power cycle. Somehow whatever code did that was messing with the content indexer