[Mesorah] arayos in Chpt 18 and 20

[Sholom Simon via Mesorah]

Sholom u'vracha,

In Perek 18, the arayos have a stuma between each pasuk (except the 
last one or two).

When they are repeated in Perek 20, all of them are listed in the 
same paragraph.

Does anybody know why?  Any thoughts on this?

-- Sholom