This is expected as a statement such as
"map 0 gain" does not contain the assigned midi channel , so saving and retrieving this history will not re-connect a midi channel to a control (ie. gain).
It would be extremely useful if I was able to set the midi channel I want to connect to a controller. F.e.:
map 0 gain 1 10
this could potentially connect "gain" of FXid "0" to midi control #10 , on midi channel #1).