Linuxcnc 2.9.x and Glade GTK3 display issue

Just upgraded to 2.9.x from 2.7.x i am in the process of recreating my glade window with gtk3. All worked good in 2.7.x and gtk2 but now with 2.9.x and gtk3 this code below in my ini file deletes the the box_vel_info but does not start the motion_control_test.ui
not sure what is going on. help is appreciated

EMBED_TAB_NAME = MOTION CONTROL
EMBED_TAB_LOCATION = box_vel_info
EMBED_TAB_COMMAND = gladevcp -x {XID} motion_control_test.ui

Please start linuxcnc from the command line and check the output there. 
You will see there the error that does stop your panel to be embedded.

Norbert