gtk_accel_groups_activate (called in gtk_window_activate_key) returns FALSE even when it finds a shortcut and activates it.
This happens because the accelerator callbacks return void instead of gboolean. I'm guessing that void is being interpreted as FALSE, so the event is propagated to the terminal which in turn leads to the bugs described in the linked issues (#159 (closed), #153 (closed)).
Edited by Sergios - Anestis Kefalidis