Not sure if this is a bug so I wanted to start first in the forum.
I have several dropdown elements on different forms and I noticed that (sometimes) these elements will disable themselves. It has happened before or after the dropdown element is selected.
I had the same issue when I was copying them. For some odd reason it was converted to a different element all together. I think it changed itself to a search element instead of a drop down. Is that what you see too? It looked disabled to me too but it was actually a completely different type of element after the copy and paste.
That’s possible. I have had weird issues on Safari as well. Had to switch to Chrome. If you can repeat the issue consistently then I would file a bug report.