Purview EXPORTS unreliable and missing "Top-of-information-store" folder

Hi Prathista Ilango​.  I'm exporting emails from 8 custodians, many of which are in the common email threads.  So it seems odd that this only happens to half of them.  Also, the emails ARE there, but the issue is that the TOIS shows up as a "calendar" folder, so it doesn't show up when you are in the "email" folder.

NOTE - this only started 3 weeks ago.  It feels like another situation where a change was made and we're left to try and figure it out.  Luckily, enough people are talking about this issue and pointed me to look at the calendar.