OK, just got around to updates.
I installed the TT 1.11 which seems to work fine, and indeed does NOT reject the MP.STOP x command like it did with the beta version.
HOWEVER it still does not affect MP. And neither do any of the II MP commands.
(while the II commands control the WW and ES just fine.)
As a test I have installed the previous version of MP, and TT II commands work fine with the previous version of MP (which perhaps rules out the faulty ribbon connection as a cause of the problem).
Re-installing the MPv.2 makes the II TT commands stop working with MP.