Loud crackling noise only on bluetooth phone calls. Streaming TV or music is clean with same devices.

I'm using an iPhone 12 Pro Max with a new set of Bluetooth enabled Kirkland 10.0 hearing devices. I have no issues with these devices on any music streaming or TV streaming through the ROKU app. And until a couple of weeks ago, they were fine on Bluetooth phone calls as well. But now, on phone calls ONLY, the other voice creates horrible crackling sounds, with various other callers including from another 12 Pro max user. All the calls, as well as the streaming is via a mesh wifi system to the phone and then to the aids via Bluetooth, but the same system was in place when the Bluetooth phone calls were clear. Maybe an ios update--if there was one-- could be the culprit?