I did some more playing with this and found that if I clear layer
selections before and after my plugin with the custom map tools is run the
system does not crash. I had looked at the crash output when running qgis
from command line and found an error suggesting symbols not found so I
suspect that
I'm developing a custom application as a python plugin for doing in-person
map based interviews with indigenous people. For this I need custom map
tools for drawing and editing map features so I can do some additional
processing, when map features are created such as recording the time stamp
(as