try the preview once with ctrl button pressed, this resets the files for preview.

Temporarily disable the antivirus and firewall (if you have Avast antivirus it is most likely Avast giving you that preview problem) so you know if that could be the problem. Also you should know that if you are connected to a LAN and use a PROXY you may have problems with the preview.

it does not help with ctrl F5 preview does not open normally. You can see the preview in the windows field and it is empty

Not ctrl F5, just ctrl key then press preview.

Alex, if Andre's suggestion does not fix it (and you have either disabled or temporarily uninstalled 3rd party AV/malware/firewall/vpn, etc), could I ask if you happen to be running dropbox/one drive, etc and actively synchronising with the cloud?

For what it's worth when I open a project if I immediately select preview I get none. I have found it necessary to be in step 3 or step 4. Is this relevant?