Can't record phone calls in lockdown mode

When I turn call recording on my iPhone 16 Pro running iOS 18.2 (22C152), it says "This call is being recorded." Within a second or so, though, it says, "This call is no longer being recorded." The feature works fine when the phone is not in lockdown mode. And nothing in the info on lockdown mode says it will disable call recording.

Any idea how I can get it to work? Thanks!