open dwg

Why is it impossible to open or reference attached dwg in AECOsim? : Grondplan SANITAIR tramwerkplaats.dwg
(other dwg files are opening/referencing well, but all these from a specified subcontractor are giving trouble)

the file opens in ACad and Brickscad without any problem (created in ACad2014)
in AECOsim ss4-ss6 it creates always an stack overflow and program crash
we need to attach these files
xrefs in the file are not the problem, opening with or without makes no difference.

who know haw to fix this,
what can we say to our subcontractor to make the dwg files usefull
what do we need to read this files in AECOsim

tried in SS4/SS5 and SS6 bim081109593en / bim081109747en / bim081109807en (win7 64b)
tried to purge the dwg
tried to install ACad civil object enablers

nothing works

regards Rik