Apparently lazy load fixes the problem:
From P4VS - Helix Plugin for Visual Studio - Visual Studio Marketplace :
> Tools -> Options -> Source Control -> Perforce General.
> You need to uncheck the previous 2 options (Treat file/folders and Preload file states) to enable the Lazy Load of file states option.
> Helix Core - Data Retrieval
Warning - I haven’t tried it myself yet because I’m away from my UE4 development computer