Alex Pankratov :
Jul 21, 2017
No idea, sorry. Not a known issue either. There's no code in Bvckup 2, beta or not, that could do something like this.
My only guess would be that you are actually looking a system freeze due to a buggy driver, in which case (a) there could be something of relevance in Windows Events log (b) it's likely to be caused by a 3rd party component that shims itself into native Windows file system stack, including "search optimizers", "malware shields", antiviruses, etc.