All that time spent double checking the TMS1100 code, it wasn't that. The problem was not that some of the games had backward controls, they all did, and I hadn't noticed. So that's my own stupid fault really.
The reason was simple enough ; Dan's schematics are either wrong or from the back perspective .... so all the wiring is back to front and upside down, so when I used those connections (it is correct in the MV technical document) unsurprisingly everything came out the wrong way round......... the CPU core always worked fine.
So, anyway, after all that idiocy I will implement the rotary control - Block Buster works fine but you can't actually play it and you can't remove the control.
A consequence of this is, I think , the O-PLA is doing the job of reversing the output on cartridges other than Vegas Slots.
This is kind of understandable. The LCD Datasheet does use "Data 0" "Data 1" "Data 2" and "Data 3" for its connectors, but they are the 'wrong way round' from normal, e.g. I think Data 0 is actually the most significant bit. I wonder if somewhere in the early development of these games - which would have been on a separate machine without real test hardware I guess - someone made that mistake.
