The Chida (Moreh B'etzba 6:190) writes " This is a Klal Gadol.
You should not follow any Minhag* unless
1) you know the root (source) of it from Chazal,
2) or authentic Kisvei Arizal,
3) or you know the true reason behind the Minhag".
* Perhaps, the Chida was not referring to Minhagim that has been in
the family for generations - your parents had from their parents etc, אמבצי
As far as I know, Shlissel Challah is none of the above.