Cloning units

In this game i managed to clone my stack of units with the general here it can be seen in the screen shot:

however after a turn the cloned units dissapear like they never been cloned - all the moves i made with them were for nothing

Can people see the units?

Yes they saw it and asked me how i got 2 generals

Similar thing happened to me (twice) in a casual game. I ended turn and logged out, then logged in again and found duplicate units. Both times, there were transport networks involved and the duplicated units were the ones being transported.