Mythic Mistress fight adds 60 seconds of no damage done to begi

Warcraft Logs
1

For some reason, our mythic mistress kill log has 60 seconds of “fight time” with no damage done added to the beginning. The fight should be around 7:27 in length but it’s instead 8:27.
Here’s the log:
https://www.warcraftlogs.com/reports/wr2NVaWFCczfgJ7A#fight=13&type=damage-done