I think this may be an issue with the M9. The fact that, as far as I know, the M9 only has 24 (4*6) patches and it stops working at 12:2 suggests that this may be the case.
You should probably talk to them – we are not experts on their fine products.
See also http://forum.tcelectronic.com/topic/7498/gsystem-line-6-m9-are-they-midi-compatible/ for more discussion on this topic, especially the comment by Mr jaded1592.
