How to Create an “Open file” Calendar Alert in a Recurring Event that Sticks

I recently wrote an Automator workflow that asks me if I want to check the arrival of the next bus and opens the local transit system’s bus stop arrival web page that shows the live time the next bus is expected to arrive at the stop I saved in the workflow.  I then created a recurring calendar event in the Calendar app that opens the Automator application I’d saved.  (I could have created a cron job, but I like the ability to easily adjust the alert time if I need to leave work early.)

The alert is a custom alert, which I selected to occur “at the event time” and “Open file…”, for which I selected my bus Automator app.  I quickly noticed that at some point in the week, the alerts on all my recurring events change to a default of a simple notification with a sound occurring the day before.  The first time I missed the bus, I discovered the problem and edited the event to fix it.  But it kept happening, and happening.

TL;DR: The procedure is at the bottom of this article.