Why does this happen? Extruding a section of double track, more often than not the right hand section renders invisible. If you delete it and try to extrude as a separate single track the error persists. The only workround is to "trim" a short section off the preceding track then it seems to work. TS was doing this when I last tried to build a route in 2014, so seems nothing has changed! No wonder I switched to route building in Trainz…
Appreciate the response but that just covers basic stuff which I'm well aware of having built quite a number of routes in RS/RW/TS over the years. It does not cover the issue of track sometimes failing to render when extruding multiple sections...