Dear Pekak,
That is not the request. Maybe you can provide a sustainable answer.
I was told by one group that their siddur that was written by their Rebbe almost two hundred years ago, does not have tachanun by Mincha. I thought that was silly, because some older siddurim only print it once and your supposed to turn back. Anyways, I found a siddur from that group that had it printed by Mincha. One chassid told me he has a copy of the original siddur. Nobody else cared. After a few months, he finally lent it to me. It had tachanun by Mincha. And mentioned very few days that tachanun is omitted. They still did not care. And, when asked, they still claim that it is not in the Rebbe’s siddur.
What really bothers me, is their lack of confidence to just saw this is how we do it now.