My VM:s freezes for seconds

When i see the problem (ZFS, ) with VS 4.0.0.278 i downgrad to VS 4.0.0.256

For the downgrad i deinstall the VS 4.0.0.278
Then i install the VS 4.0.0.256 manual.

VS 4.0.0.256

With the VS 4.0.0.256 the problem (zfs, …) is gone.

Same Days later i install manual the VS 4.0.0.280 without a problem.