Steps to reproduce:
1. Create a series with multiple events (four works for me)
2. Enable OAIPMH republication
3. Update the series ACL
4. Check the OAIPMH Records of the events for the series ACL
-> Most of the time at least one event still has the old series ACL. Since this is a timing issue, it can be hard to reproduce this on some systems, though.
The cause for this bug are the two snapshots that are triggered for each event when the ACL of the series changes, resulting in two download distribution jobs to OAIPMH being started in almost the same moment. When the first job distributes the series ACL after the second, it will redistribute the old version, resulting in a lost update.