Pagefile Issues

Hello folks!
I'm in trouble with pagefile / virtual memory related error dialogs on a hand full of different (productive) machines, all happening since their upgrade to Windows 10 Pro.

On all of them, paging behavior is set to Windows defaults.

RAM is 8 GB each, but won't be used more than 40% while running into "Virtual memory low, close program [insert any common app you want]"-errors.

Interestingly, pagefile.sys goes up to whopping 14 Gigabytes, but not further (why?).

"Resetting" its size to "No pagefile at all" and then "choose automatically" it has then a typical size of just below 2 GB, but after a reboot - without starting any app or program - it is again breaking the sound barrier of 10 GB.
There is way enough (SSD) disk space (50+ GB) for more virtual memory, but never taken.
All boxes run Windows in x64-Mode.

What did I do wrong?

Thank you soooo much!

Cheers
Kai