Materials not rendering correctly

[loofer]

I have a weird issue that's got me stumped, in the attached image I'm rendering a building and it looks fine in the vray frame buffer (vray 3.7) When I save it as a .png and look at in a picture viewer one material is coming out mostly black, when I bring it into PS the black areas are transparent but also the transparency affects the matid and wire colour layers too. I looks like it's only saving specular highlights and not the diffuse part but I'm not rendering out in elements. If I save as a jpeg or .tiff it's fine but .png it's stuffed. The settings for the soldier course brick seem the same as the running course which has the issue and I had no issues when testing at lower res, anyone have any ideas?

[loofer]

I'm a tool, I had 'All channels' selected in the reflectance section instead of 'Colour only', I'll leave the post up in case anyone makes a similar mistake.