My team's app was also seeing this issue on iOS v15.4.0 and above. I've opened both a Technical Support Incident and submitted the bug via Feedback Assistant.
From the TSI I got the response:
"Our engineers have reviewed your request and have determined that you are experiencing a known issue for which there is no known workaround at this time."
Knowing that there was no native option, my team ended up using Twilio to route the call and spoof the callback number (which is an added cost to us versus the user's phone company doing that, but a necessary app requirement).
efeder
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My machine:
MacBook Pro 2019 (16 inches)
Running: Big Sur 11.6.4
Processor: 2.3 GHz 8-Core Intel Core i9
Memory: 64 GB 2667 MHz DDR4
Graphics: Intel UHD Graphics 630 1536 MB
I noticed I've had this issue if there is a specific process taking up a lot of CPU. If you open Activity monitor, you can see which process is taking over 100% CPU. By clicking the X to stop the process that is taking up the CPU, that mitigates the issue for me.
Often for me it is the kernel_task, and it is related to my USB-C connected dongle/monitor. I will also notice that those connected cables can get hot. So when this happens I disconnect all usb-c cables except for power and let it sit for a few minutes. Afterward, the CPU taken up by kernel_task goes down to a more normal <10% and the crackling goes away.
Same issue here. My app functionality is broken for this -- I allow users to make calls with their caller id blocked by prefixing with '67'. I've tried manually encoding by replacing '' with '%2A' but it still does not work. Has anyone opened a Technical Support incident?