I can confirm this is still a problem on v.0.39 and v.0.39.20-beta. This issue happens to zuyin eten as well.
The problem exists with multiple character selection; in other words, when you input the phonetics for a few words together and then you select the whole required phrase/statement, the bug happens.
On the contrary, if you only input the phonetics for one word/character then you already select the require word, it will not duplicate.