This has been a issue with us too, although our case is with our subscribed Taylor and Francis journals. They have a lot of "digitally published, ahead of print" articles, which have to go through 15 mo. embargo. We do subscribe to these journals, but since these "digitally published, ahead of print" look like they are published already on ExLibris side, they mistakenly "get out of" embargo, 15 mo. after "ahead-of-print published" and make available in Summon.
This has been a issue with us too, although our case is with our subscribed Taylor and Francis journals. They have a lot of "digitally published, ahead of print" articles, which have to go through 15 mo. embargo. We do subscribe to these journals, but since these "digitally published, ahead of print" look like they are published already on ExLibris side, they mistakenly "get out of" embargo, 15 mo. after "ahead-of-print published" and make available in Summon.