Sorry for the bad english, but heres how i fixed this bug on my mate de, thanks @glisign for the hint. As i understand, this issue is caused by ibus input framework (enabled by default in ubuntu mate variants) which reads your raw input and interpret them to non latin character if you enable their respective language support. But in this case, transgui reads both the raw input and the output character that ibus spits out (in this case just latin character map 1-1) thus doubling the keyboard input....
this issue is caused by ibus input framework (enabled by default in ubuntu mate variants) doubling input keys after "killall ibus-daemon" this problem was resolved on my Ubuntu Mate 16.04.1 system