Hi guys, thanks for CC me in @john_drivenupthewall. . As mentioned previously Colin, I need to see the original file so I can figure out what is happening, yet looking at the file you have attached it appears as though either the file has been exploded and materials have been made unique & I can only assume this has been done by a Plugin, (as it is very unlikely the end user manually made materials unique 4000 times).
There is also a chance that the user exported the model and then reimported the model, or used a rendering engine that has a plugin that explodes and makes unique but I do not know for sure. One thing I am 100% sure of is PlusSpec does not replicate materials. Colin PlusSpec has a built-in Purge tool, in fact, I ran the purge tool, and it cleaned the materials up in 2 seconds, that is longer than it took to open the file. Mate, ideally, the client reaches out to us, as support is included with PlusSpec.
The easiest way to get to the bottom of it is to tell the client to 1 restart SketchUp using a blank template, (no material or components). Then draw several walls, add a window roof rafters and trusses ect etc and then see if the materials are replicated. I can tell you now they are not.
I can not tell you why Mac opens slower than windows, there are many reasons I do not use Mac and this just added one more to the list . In saying that we have many Mac users and not one has ever come to me/us with this problem.
Sorry mate, I can not help you out on this one. I’m sure if you talk with the client, you will get to the bottom of it.
BTW I tested a large model OBJ and 3Ds export and import on SU 19 and I could not replicate the issue on Mac or PC