I use mlterm in genuine mode and spawn a lot of mlclients.
Sometimes, when I try and close a lot of them at the same time (for example), some won't close.
If I open a mlconfig (gtk) on the non closing window or on another one and then click "cancel", it may close.
Sometime, I must search for the right window/mlconfig to be able to close my window,
sometime I must wait until I restart mlterm, usually once a day where possible ...