This happened to us again today. Members of my team imported lists into the event programs to process and anyone that was new, never showed up in the SCHEDULE tab of the smart campaign to process the attendees/MQLs. The response we received from Support is similar to what we were told in the past:
This is due to a database issue that you've experienced before. I can escalate it to engineering to get it fixed for this list but that can take some time. Since it's urgent the quickest way would be to resolve - instead of referencing “member of list” in your smart list - is to copy/paste the specific email addresses for those leads into the smart list of the smart campaign. I have overridden the Smart List processor so the campaign shows the members correctly. I am going to create a case with Engineering to get this resolved.
The workaround they mention can be very risky if you have duplicates that exist in the same or other partitions (based on how Marketo determines the ACTIVE lead - see Re: If duplicate leads are an issue, be aware of how Marketo determines which lead is active ). This ongoing issue continues to hamper my team’s ability to use Marketo effectively across our global organization. The move to the Google Cloud can't happen soon enough.