This may be addressed later as I'm still catching up but I had a thought. We were discussing if the Witch King had been blown out of his cloak by Frodo on Weather Top and if this meant a temporary uncloaking. Pure speculation on my part but what if the Witch King had been truly uncloaked? If I recall correctly they don't run into the Ring Wraiths for a while afterwards. So my theory is that the Wraiths, having the power of Sauron in them, are capable of re-cloaking each other if at least some number of them are available. Perhaps how long this takes would depend on how many still cloaked Wraiths are available to help.