Application randomly crashes to errors like:

(mawe.py:10556): Gtk-WARNING **: /build/gtk+3.0-2Ut_nl/gtk+3.0-3.18.9/./gtk/gtktextbtree.c:4034: byte index off the end of the line
(mawe.py:10556): Gtk-ERROR **: Byte index 1362 is off the end of the line
Trace/breakpoint trap

(mawe.py:8467): Gtk-WARNING **: /build/gtk+3.0-2Ut_nl/gtk+3.0-3.18.9/./gtk/gtktextbtree.c:4034: byte index off the end of the line
(mawe.py:8467): Gtk-ERROR **: Byte index 451 is off the end of the line
Trace/breakpoint trap

Examine possible reasons.

Update: Problem examined. It looks like it is related to hidden regions. Hiding a scene and moving mouse over it crashes the application quite quickly. Related question in stackoverflow:

https://stackoverflow.com/questions/59190178/gtksourceview-buffer-crash-gtk-error-byte-index-is-off-the-end-of-the-line