Zoom Tool not zooming/stuck

Hello,

I have had this issue since a while now - I'm trying to zoom into an image to edit details, sometimes, it works flawlessly, sometimes I can press Ctrl-Space till I'm blue in the face, nothing happes, the too doesn't switch, LR (not the system) appears frozen for a couple of seconds. All I can do is wait until it zooms into some arbitrary location.

Is this because full size previews have not been creted? I always used to have that on, I just looked into the catalogue settings & prefereces and couldn't find anything on fiull size previews except on how long to keep them.
Edit: I just tried zooming out of the next image I clicked on (was automatically zoomed to 100% after being at 100% on the last image) and it took 5-6 seconds to react.  Zooming back in took close to 3 seconds. 

Latest version of LR (14.1), Win 10, Quadro M5000 on Auto, 128 GB RAM, all M2 key SSDs

[moved from bugs to discussions according to the community rules - Mod.]