I have noticed this randomly through the last 3 versions (Currently on SR23).
Sometimes, when selecting leaders, dims, ect within the layout space, the highlight does not go away upon deselecting. The only way to un-highlight these objects is to exit Rhino and re-open the file. This is a non-issue except when going to print, these objects will not show up on the print until re-opening Rhino.
This bug seems to be intermittent through our drafting pool with no real trigger. The drafters do use remote computers to perform their work, so I am wondering if others with dedicated local computers run into this issue as well.