If you can find any error logs near the times time when the repeatings occurred executed successfully last time, please create new support ticket with details. The logs are written to the log subdirectory of your Jira application home directory (or elsewhere if you have configured a different location). File: atlassian-jira.log.
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From version 3.5.0 the app has feature to check and report for interrupted repeatings. It is a scheduled job that runs every night and is searching for interrupted entries. When any exist the the email notification is sent to Jira administrators. These checks also try to re-schedule again such repeatings automatically. The job also print the check result in Jira logs with INFO logging level. Please read following How to get more logs from the Repeating Issues app?.
Codedoers suggest you to have always the the latest Repeating Issues app version.