[Avodah] What is the source for the minhag of Chasidim to have HaKafos on Shmini Atzeres night?

[SBA]

From: "Micha Berger" <>
In the second post RSBA writes:
: To have even a hava amina that the "basis" of a minhag practised by
: tzadikim and kedoshim and thousands of their followers over centuries
: is "due to a mistake in transcription" is ludicrous and mischievous.

It's not so rare., the Torah Temima's  theory about the origin of saying
"migdol" in bentching on shabbos.. was to contrast the text of
bentching with that in Shemu'el beis, and therefore read "besh"b 'migdol'".
Somone then expanded the rashei teivos to "beShabbos" and so the minhag was
allegedly born... the theory doesn't work because the Avudraham mentions the
practice, and he didn't know about a future splitting of Shemu'el ..
>>>

I am unsure how a mistaken REASON (or theory) for a minhag is the
same as claiming that the minhag itself is based on an error.

>See the mavo to haAqov leMishor by R' Dovid Cohen for more examples. If RDC
>does it, why can't Yaari?

I can't find my copy of that sefer right now.
Can you give us some of his examples?

SBA