I'm currently having the issue in Moodle 3.10.0
It's happening in several - actually I think all - of the anayltics models emails that had been turned on. Those were "Students at risk", "students who have not accessed the course recently", and mostly importantly for us "Upcoming activities due" since that one goes to students.
We don't have any template/message customization but we moved. our Moodle hosting this Fall to Azure. Is there something in the way our Moodle is hosted in the cloud that is causing these broken location links?
Let me know what additional info I can provide.