Consider this: a form view with a one2many list view. In the one2many
list view, there is a many2one field. When opening the manyone in a
modal form view, there is a many2many field. In that situation,
clicking on 'Add a new record' on the many2many field had the
unfortunate effect of interfering with the one2many field in the main
form view, which caused a crash or the modal form view to close
unexpectedly.
The issue is that an event was simply not properly stopped at the proper
location. This is usually not a big deal, but, as described above, it can be
a problem in some cases.