[Mesorah] kikar / kikar

[Sholom Simon via Mesorah]

The psukim at 25:39 and 37:24 are almost identical.

The first word, in each, is kikar (zahav tahor...).  In both cases, 
there is a tevir under the second kaf.

But in the former, the second syllable has a patach; and in the 
latter, is has a kametz.  I can't find any mention of this in my tikkun.

Thoughts, anybody, as to why this is so?

Good shabbos!!

-- Sholom