Okay, one more post on this. It's good news and bad news…
The good news is that, at the moment, it looks like I've actually solved the problem, simply by toggling clipboard history off and on again.
The bad news is that I doubt I actually have, because I am pretty dang sure I did that before, and I strongly suspect there's an unknown trigger for the bug and it's just a matter of time before it's back.
But I have just tested interactions between LaunchBar and about a dozen other common apps, and clipboard history has remained fully functional thus far.
I will be vigilant going forward. If my clipboard history starts misbehaving again, I will hopefully notice quickly and have some idea what triggered it.
UPDATE: Sure enough, the problem soon returned, after only a few minutes of quite ordinary productivity. I have no guesses about the specific trigger. Worse, when the problem return it behaved differently and worse than before (the workaround described above, invoking the history between copies, stopped working).
Last edited by bigcloits
on Thu Nov 29, 2018 7:14 pm, edited 1 time in total.