64 bit. I actually ended up purchasing the Microsoft app version after having issues with the one offered on Sourceforge - both have issues.

I just tried the older version and it spikes to 90%, but not 100%

Seems there's a bit of an issue there as well for me.

The spikes below start when drawing one wall and simply moving the pointer across the screen. The 90% level is sustained I opened the Modify Wall dialog.