Ran into this one today. Open a file that has linked blocks in it. Double click on a block and let it open in another session of Rhino. Save the linked file and close it. When I’m sent back to the original file with the links in it, everything looks ok for a couple seconds and then poof! Everything is gone - deleted - everything. Except the block links still show up in the block manager. All models, lines, dimensions, in both model and layout space gone. make sure your Rhino file is saved before opening any of the linked blocks in it. Fortunately, updateselectedblocks still works fine.