merging and deleting causing crash

I've made a simple plugin to manage loading and deleting of specific data in a
scene  and it seems to work fine when running in debug, but in release it will
crash.  The basic functionality is that it will merge an fbx in, tag it with a
user property, execute a python script and then eventually delete the imported
data when the user specifies.

It doesn't seem to be consistent at the point when it crashes, it could be
either on a load or a delete operation and since it doesn't crash in debug I'm
having a hard time determining what's going on.

Does anyone have any ideas?

thanks