Did this ever get resolved?
I am experiencing a very similar thing. (latest stable and beta versions tried, uninstall and reinstall etc etc all tried. I first experienced this a few months ago but decided to ignore it, but my latest attempt recently had the same problem)
If I install the Ordered File Placement plugin, and set it to rebalance existing files across my 20 odd drives, it gets stuck on calculating indefinitely, with a big percentage (13%) of the CPU and around 50mb and growing of RAM tied up. It never finishes, and eventually the service seems to get totally stuck (it won't restart in services.msc, it says that the service didn't respond properly to the request) and the pool drive becomes unaccessible. The only option is to turn off the "rebalance existing files" option, and reboot. Then everything goes back to normal.
It's clearly something to do with this plugin and the rebalance existing files option as this thread previously found, but I can't seem to make it work no matter what I do.
Any suggestions?