thanks Steve !
to sum up :
Win 10, Monitors :
Main 43" / scaled 150% ( 4K screen - HDMI )
Secondary 27 " / scaled 100% ( 1080 screen - VGA )
i have a lot of third party plugins ( even bridged old 32 bits )
Backbone is the only one crashing cubase.
i got a stable state with :
Cubase HDPI = OFF
Backbone HDPI = OFF
disableing this fix
https://forums.steinberg.net/t/cubase-10-5-hidpi-on-windows-10/149114/18
( = going back to normal : uncheck "use this setting to fix scaling problems… " + uncheck "override high DPI scaling… " )
And turning this OFF >>
NB : that was NOT turned off when the crash happened ( for crash dump analysis ).
in windows settings :
settings > display > advanced scaling settings > “fix scaling for app” = OFF
( this was also the culprit of cropped plugin windows in my secondary display )
In this state i still have the cubase menu ( from the top menu bar : file / edit / projects … )
not showing at the right place & font size … but it’s manageable
And i don’t have plugins opening with crazy size.
So all HDPI off is the way to go it seems
NB : this is a brand new PC ( from 3XS - optimised audio workstation ) , fresh win 10 install,
dedicated to only DAW work
I cannot upload any crash dumps as the maximum size seems to be 4Mb and my crashdumps weights 11.1 Mb,
hahaha… 