Multiple "OS X Base System" mounted / system freeze on disk operations

Hi,

I'm running macOS High Sierra 10.13.3 (17D47) on MacBook Pro (Retina, 15-inch, Mid 2014)

I recently started to observe complete occasional unexpected system freeze on disk operations. I.e. at some moment UI continues works, but when app needs any load/save, even if I switch to terminal and run `ls`, app freezes. After several disk operation attempts (i.e. several apps requires disk access and frozen) seems that some disk queue overfills and system freezes with flower cursor. Then I can switch between windows, some of them update their content (except for windows waiting for disk) but I can not do anything in any windows that require disk. Only hard reboot helps. I think it started when I upgraded to High Sierra and it happens one-twice per month completely random (as I observe it, but I believe there's reason for that).

For the reference, I never reboot my mac except for situations like this or system updates.

While investigating problem I opened Disk Utility and observed huge number of mounted "OS X Base System"

Initially it is one or two, but while system runs I can observe up to a hundred.

Any idea is multiple "OS X Base System" is an issue?

Any idea if it can be connected with system freeze?

Thanks!

Screenshot for the reference: