Previous sites are not available if there is a site without any events in the previous sites model. The Operations.populate_model method works from most recent site to oldest, and the model building errors out upon encountering the site without events. Upon opening the dialog, any sites created prior to the "0 event" site will not be available in the previous sites drop down.
Here's what it should looks like after a potential bug fix:

Events records are created when clicking the play button for a drop/ctd:

Previous sites are not available if there is a site without any events in the previous sites model. The Operations.populate_model method works from most recent site to oldest, and the model building errors out upon encountering the site without events. Upon opening the dialog, any sites created prior to the "0 event" site will not be available in the previous sites drop down.
Here's what it should looks like after a potential bug fix:

Events records are created when clicking the play button for a drop/ctd: