Badminton String Tension Maintain?

Hi All,

I recently (15 Mar 14) string (BG66) a racquet (Lining) with digital tension of 25

First few weeks, the hitting feel, sound and smash are very promising

But after that (3 Apr 14), the tension no longer giving me such feel anymore

Is there anything to do with string method? or the closure tie up is not good?

I tried other shop and the tension maintain till my string is broken

May need some help over here

Thanks,
Gary