Missing Overlays in Editor

Hi,
I’ve created a bunch of overlays on each page, at least 4 per page. Some of them simply disappear from the editor making them impossible to find and edit. They are ‘there’ as they work on the site, but on some pages they’ve just randomly started disappearing.
Previously, Sitejet has bugged and reset the height of these overlays to 0px and I’m wondering if that’s happened again, but I’m unable to locate them this time to find out.
Any ideas how to find lost elements?
This is the preview site showing all overlays are working: http://1df4e3-502b8.preview.sitejet.io/

Missing overlays in back-end are:
Brand Materials page: All top 3 overlays
UF Perspectives page: 2nd and 3rd overlays on top row

Thanks