Its not going to be worth testing without images, IF images have a part to play, as mentioned in the notes with the upload, I have been working with MANY images in a file for years and never experienced this, exporting out objects and some images to leave behind any gremlins of this file and carry on working with a fresh file, sees file go HUGE, .
Difference with this file was adding a mesh, always makes it SLOOOOOOOW, then deleting mesh and the jpg from the obj didnt have much effect.
I have spent an hour or more finding all the images, thank god I put the image file name in the layer !
I had those images and the .3dm files in the same folder, different to my normal workflow, so they should all be seen.
Steve