[Mesorah] trope question on Bereshis 1:5 & 1:10

[Sholom Simon]

An acquaintance asked the following question:

>In verse 1:5 is the phrase "v'lachoshekh KAra lailah" (emphasis in
>kara is on the first syllable per the trope).  Later, in what
>seems like parallel construction in 1:10, we have "ulmikveh hamayim
>kaRA yamim" -- emphasis in kara is on the second syllable.  Both
>phrases are the same trope in the same family -- the "kara" is
>munach in et nachta.  I checked multiple sources, thinking this
>was a typo, but apparently not.
>
>Why the difference?

Any ideas?

-- Sholom