One more learning along the way today -
I put the Bluebeam information on layer 'LATERAL'. Yesterday I had also drawn some other information on this same layer, so Archicad native lines. This morning I reimported the original in an earlier attempt to fix this. this reimport seems to have deleted all the Archicad native lines when this operation was done.
So consider whatever layer the Bluebeam data is on as sacrificial!
AC19-23 | Win10 Pro | i7-8700K | Quadro P600 | 500gb 960 EVO M2 | Dual 28" 4k Samsung U28E590