Freecad freezes when opening large STEP-files

[sterna]

I have a problem that when I import a large STEP-file (>70MB) into Freecad, it becomes unresponsive after a while. Importing smaller STEP-files works fine (takes a lot of time, but that's expected). I don't know if the file is broken or if it's just very complex. I can unfortunately not share the file, as it is a secret file form work.

What happens:
I import a large file into Freecad. Freecad processes for a while (5-10 minutes, as expected) and then the model shows up in the GUI. At this point Freecad enters a weird locked state. I cannot manipulate the model at all, and I cannot check anything in the model (I cannot click on any element or perform anything from the toolbar). Freecad consumes almost no processor power in this state.
What I can do, is to use the menus in the top of the window. Through this, I can as a workaround, save the file as a Freecad project file, fource quit Freecad and then open the file again. After this, everything works as normal.

Freecad information:
OS: Mac OS X
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.9803 (Git)
Build type: Release
Branch: (detached from dd63fe9)
Hash: dd63fe92107a87f6003f33518e387743a2090a1c
Python version: 2.7.13
Qt version: 4.8.7
Coin version: 3.1.3
OCC version: 7.0.0

System information:
macOS 10.12.3
Macbook Pro (13 inch, early 2011).
2.3GHz Intel Core i5
8GB 1333MHz DDR3
Intel HD Graphics 3000, 512MB (builtin)