AGOL Basemap Masking Operatioall Layer

Hi folks,

I am using the Terrain with Labels basemap from AGOL in my Flex 3.2 application. Along coastal areas my operational layers are being masked, apparently to create a bathymetry affect, screenshot attached.

Is this a know issue, is there a remedy? Why would the basemap render over the operational layer?

Thanks.
PW

edit: Apologies for the typo in the title, *Operational*, guess you can't edit the title...

Attached Thumbnails