- when switching note (sometimes)
- autosaving changes in a note (sometimes)
- closing a notebook (most times)
- Exiting the application (most times, the error dialog also prevent windows from shutting down and this result in many such dialog windows (1 every 4-5 secoonds, so it can be 20-30 or more if you try to address it instead of choosing shut down anyway).
I usually have 2 or more notebooks open, sometimes 4 or 5, most of them small but one is about 18MB and another at 400+ MB (with lots of images embedded in the notes). The bug seem to happen more often when one or both of these notebooks are open, but may also happen when only the smaller 2-3 MB notebooks are open.