When executing the Publish action within the pages app, you can (quickly) click on the 'SAVE CHANGES' button more than once before the 'Submit for publication' dialog is submitted.

This will result in more than one publish request, one of which will fail due to no 'version' being found in the JCR:

javax.jcr.version.VersionException: Version {}1.100 does not exist.
at org.apache.jackrabbit.core.version.InternalVersionHistoryImpl.getVersion(InternalVersionHistoryImpl.java:277)
at org.apache.jackrabbit.core.version.VersionHistoryImpl.getVersion(VersionHistoryImpl.java:138)
at info.magnolia.cms.core.version.BaseVersionManager.getVersion(BaseVersionManager.java:335)
at info.magnolia.cms.core.DefaultContent.getVersionedContent(DefaultContent.java:500)