Just as the title says, when you have an expression map enabled, regardless of the settings implemented there, the output port of a midi send FX in on the same midi track (post, no midi effect set) sends CC 123 with a value of 127 every time you change the position in the timeline. This seems like an erratic output of an internal routing in Cubase, as it makes no sense at all that this would be sent. I am on Cubase 8, Mac OS X.
Can you confirm that? Looks like a bug.