I'm in the iOS Beta program, and I noticed after the last update that there were multiple birthday calendars listed in Calendar and Fantastical (my preferred calendar app). When I first noticed this problem, I had around 135 extra calendars listed under "Other" and around 8 under Facebook. Since then, the calendars under "Other" have increased exponentially; I now have well over 2000 Calendars in this section. The large and growing number of calendars means my phone slows to a crawl or freezes completely whenever I try to access the Settings on my phone.
I've tried disabling/re-enabling Calendars and Contacts on my iPhone, I've tried a hard reset, and I've even completely wiped my iPhone and reinstalled the apps from backup, but the problem persists. Luckily the problem doesn't seem to affect my iMac or MacBook Air, so it leads me to believe the problem has to do with the latest iOS beta and iCloud.
I really depend on my calendars to keep me on track, so not having access to them is a huge inconvenience. Is there any way to force delete these "other" birthday calendars on my device? I'm using iOS 10.1 on an iPhone 6 Plus.