Terrain system off incorrect simulation.

[CptVsevolod]

So I found multiple inconsistencies with the real thing in terms of TERR SYS off simulation. As shown on the attached image when TERR SYS is off the VD stops displaying grey shadowed area and the legend “NO TERR AND WX DATA AVBL” appears. 
Another bug happens when you deselect GNSS via POS Monitor page, NAV PRIMARY still stays displayed (real thing would display NAV PRIMARY LOST)

There is one more annoying bug: when you have TRAF PB on EFIS CP pressed and then you press Default setting on SURV MFD page, the TRAF PB turns itself off for some reason and you have to manually reengage it again.