Sherlock Holmes & the hideous scanline puzzle

[Fudoh]

For an upcoming converter roundup I'm currently going through a number of converters, transcoders and scanline units. Trying various combinations, sources and displays.

There is one particular setup combination I've run into, which I can't make any sense of.

The setup looks this this:

VGA source (e.g. a Dreamcast) > SLG unit > Kramer FC-14 transcoder > component to HDMI converter.

So far nothing special about it, except for the fact that the Kramer nullifies the scanline effect. Tried with a MiniSLG, a MiniSLG2 and a SLG3000. But hey, it gets even weirder: on a SLG3000 I can flip around the odd and even scanlines, and change the expected VGA signal polarity. When I set the SLG3000 to a certain polarity combination (usually unusable for 480p signals) I get the scanlines back. And to top it off: with this combination the Kramer flips the odd/even alignment, so setting the SLG to even scanlines results in the scanlines you'd expect from the odd setting.

I have really no idea what's going on, but I thought why not just throw it out there to see, if anybody else can make any sense of it.