Sorry for the delay in responding.
It has not been verified, because of I haven't encountered the operaion yet.
So, I removed relevant maps from latest package for now.
And I think I may have found something that might be relevant.
There are two similar maps stored in the cliant data.
(s06_Atoll and s06_Atoll_asym / lighter one is Atoll_asym, darker one is Atoll)
It is possible that these maps have been mistaken.
(for instance, #8 screen shot in above post, the island on C-D/8 doesn't exist in s06_Atoll_asym)