Oh, just noticed that mouse_left isn´t checked inside the panel_clicked function. Perhaps you could put a decision structure to check if mouse_left is true and then shift bmaps...

Maybe you´re missing to set mouse_pos?

while(1)
{
vec_set(mouse_pos,mouse_cursor);
wait(1);
}

Actually you´ll see the mousemap moving, but mouse_pos will be null, if you don´t set it via mouse_cursor.
So the engine won´t realize when you touch a panel.
Maybe this helps.