Hello,
I have had a similar problem on some models imported into 3Ds Max from SolidWorks and .step files. I would first try to apply the "smooth" modifier to the model in 3DS Max and set it to "auto smooth". If that doesn't work try to apply a Tessellate or Quadify Mesh. (I would try these on individual parts to just check if they work as they can crash the program if you do the entire model in one go)
If the issue is with the plugin crashing, I know that when I've had issues with it, it was best to re-install 3DS Max, Keyshot, and the plugin completely. Make sure to save a copy of your Keyshot resources folder in case anything goes wrong. (the folder doesn't get deleted it but the shortcut does)