@silvano this is a Rhino bug, (reported already here Dimension Shift With Detail Window Activation/Deactivation - #19 by Eugen) and also notified to McNeel: https://mcneel.myjetbrains.com/youtrack/issue/RH-65652
It happens with blocks, and therefore with VA objects too (which are also blocks).
It seems to happen when the osnap Int is activated.