Ok i've tracked down the bug, and I think it's a bug that will surely explain some previously reported rare missed clip capturing reported by others.
The problem was that CHS was detecting the case where multiple clips were very rapidly put on clipboard and ignoring such events. This avoided some degenerate behavior when some app was out of control copying stuff to clipboard, but what I suspect is happening with ZIM (and i suspect other apps on rare occasions) is that the app is sending multiple items to clipboard in quick succession, and the first item is probably not in standard text format -- resulting in CHS ignoring the first item because its format is bad, and then ignoring the second item because it was coming too fast on the heals of the first.
So.. I'll have a new beta version up tomorrow for testing. My only concern is that we'll see some reports of problems do to removing the old protect-against-too-rapid-clipboard code. We shall see.