MicrosoftMicrosoftI tested adding a bunch of exchange and iCloud contacts and found that I started experiencing delays in starting or ending phone calls at about 12,000 total contacts and saw that WhatsApp calls stopped working at about 15,000 contacts. WhatsApp was giving an error saying "Unable to initiate call, please try again"
I enabled “Allow unmanaged apps to read from managed contacts accounts” in our device restriction policy and the issues went away immediately. This is probably a better workaround than disabling managed open-in altogether.
I then disabled “Allow unmanaged apps to read from managed contacts accounts” again and the calling problems did not come back until I rebooted. Then I tried disabling all the Siri & Search settings under Settings->Contacts->Siri & Search. I also disabled all the Ask Siri options in Settings->Siri & Search. The call delays got considerably better but I still couldn't make WhatsApp calls. Waited a couple minutes and then I could also make WhatsApp calls.
Something weird is going on between managed open-in and Siri/Search functionality.
