Exporting observations in a single session works fine when exporting them as an Excel file. Exporting the session as an AstroPlanner .obs file doesn't. The attached screenshots shows the number of observations in the session which AP plans to export does not match the actual number of observations made in the session.
As the screenshots also shows, I logged observations on both the 15th and 16th of November. Both sessions lasted past midnight. I was able to succesfully export the session of the 15th as there was no session closely preceding it, nor a session following it. Now with a session present for the 16th I am no long able to export the session correctly.

Fixed.