I\'ve just updated to Xcode 9.4.1 and experienced an issue with the clipboard being cleared randomly.
So I select a text, hit CMD+C, then go to the posi
Also read in the Apple forums that closing the simulator while working fixes this issue. So if it happens to me I close the simulator and copy-paste works fine from that point forwards.
Haven't tried it yet but I have feeling that Eva's answer is correct in that the simulator is trying to sync your pasteboard.
Apple forum article
** Edit **
Can confirm that Eva's answer works and I no longer have this issue when I turn of automatic syncing on the simulator