Duplicate Entries in Subscribed Calendars

I just noticed today that I had 80 entries for a subscribed TripIt calendar.

I was about to contact TripIt support when I realised the same applied to all of my subscribed calendars.

This seems to be something that has happened in the past few days.

My version of Calendar is Version 8.0 (2092.3)

Has anyone else noticed this? It's easy to replicate:

1. Subscribe to a .ics feed

2. Choose "On My Mac" as the location

3. CMD+R to refresh a few times

If I do that I get duplicates immediately. It's very frustrating and, as I mentioned, seems to only have started happening in the last few days.

Thanks,

Joe