Dear Rhino Team,
Yesterday and today I came across a very weird bug / error in Rhino. I kept workin in some files of a previous project and wondered, why copy / paste does not work. Whenever I tried to copy an object the colourful wheel kept spinning for ages. And when it stopped and I tried to copy the objects I got the Message “Unable to paste, no Rhino objects or text on the clipboard.”
I was very confues. So I opened a new filed, modeled some stuff saved it. Copy Paste worked perfectly.
Copy and pasted the exact sameobject into the scene I worked in before and it would past. But… I couldn’t copy past it again. 
It drove me nuts.
And then I realised that there were some legacy materails from Rhino 7 that weren’t loaded correctly. Some textures were makred missing etc. So I deleted all of the legacy materials (with the / in fron) and all of a sudden it worked again.
And the exact same issue appeared when I started working with Substance materials.
So I also started deleting Substance materials, one by one. And funny enough after having deleted a few (like 6) copy pasty still took very long but started working again. Rhino also started to unpack all sorts of tiff images into various folders or even in the folder where rhino files are located. As soon as I had deleted all Substance materials copy pasty started working again like before.
I can’t really make sense of it. But maybe you can. Or maybe you have any tips how to avoid this behaviour.
Kind regards,
Tom