Sooo many hours over so many years playing this game (on iPhone). Love it.

I found a strange corner case where mushrooms-with-gem-connection doesn't offer the gem connector when scarecrow is adjacent.  The screenshot shows the situation.  I should have included another screenshot proving I had gems at the time, but please believe me that I double- and triple-checked.  (And, on the very next move, the scarecrow was killed, and I was allowed to fill in a connection space using the gem, with an almost identical enemy layout.)