Signal passthrough only outputs RGBHV regardless of the YPbPr setting

[syboxez]

I am attempting to use my GBS-Control as a simple RGBS to YPbPr transcoder, but only the 15KHz mode (and probably the other modes as well) display properly; when I switch to passthrough mode, the image becomes pink and sync gets messed up, which also occurs when the setting is set to RGBHV.