Today I encounterd the same glitch. I am 100% sure I did not change my club setting. First two rides were as default for Club Jarvis. Did no changes just jumped on the bike, selected Watopia and joined the event (Haute Route Watopia Stage 3). I saw a lot of other club members rode it and were displayed in the club events. So it was not related to the event. Can it be connection related? The WiFi signal was good enough, but not as strong as usual.
Update 20200406: Still tired from the stages of Haute Route Watopia, I started Zwift today with no intention to exercise, just to check if Club Jarvis was still selected as default and it was. So yesterday something went wrong at the server side in my opinion.