Hi, Matthew. Sorry you’re experiencing this.
Is this only happening with recurring events? If yes, does it also happen for theĀ first event in a recurrence series (e.g. create a new recurring event–once daily for a week–that starts Oct 13 –> does only Oct 13 show up or not even that one)?
Do events appear in other views and just not month view? You might try disabling Month View caching: wp-admin > Events > Display tab > uncheck “Enable the Month View Cache”
Please let me know what you find out.