I don't really understand the problem, but I know how to fix it.
The problem seems to be that the scroll pane of the CLV is slightly undersize with respect to the custom list view itself. Increasing the size by a couple of dips fixes that ...
.. .. ..
Dim sp As ScrollPane = CustomListView1.sv
sp.PrefHeight = 142 '<==== ADD THIS LINE ####
sp.Pannable = True
.. .. ..
Possibly there is something wrong in the your layout that would avoid this problem, but I cannot see it. Maybe someone else can.