[Solved] 64179 Technic Beam 5 x 7 with Open Center 3 x 5

[Steffen]

I suggest that you change your setup as this:
(a) create a model file
(b) reference 64179.dat from (a)
© reference the other parts from (a)
Then all parts should appear properly. I think that you've messed up your file structure somehow.