Offset Srf problem

(ultimate wip).
Offset srf does not run properly on this surface (I see there is an abnormality in normal directions).
Offset srf incorrect.3dm (126.5 KB)

You are careless.
Offset srf incorrect-1.3dm (210.9 KB)

snipaste20170831_170320

!snipaste20170831_171854snipaste20170831_171927