You may have a sharp spot on the top of your saddle or in the groove of the nut.
The groove in the nut might be too tight causing the string to catch and break there when tuning. Adding graphite or widening the groove will help.
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Myself Manit Dani, Guitarist / composer / lyricist of SOUL the duo.
It was june 2006 when I started playing guitar and I never knew that one day I teach people, well its an honor for me to share my knowledge and encourage people to play guitar.