Phone speaker cannot be selected if Gear S3 is connected

[android_user1]

On the Pixel 3 XL, I have a Gear S3 paired to the phone. Everything seems OK, except in the Phone app. When I'm on a call and try to switch to speaker mode, the speaker button shows the Gear S3 in blue, and clicking it drops down to show Speaker and Phone as well, but neither are selectable. I have no way to play the audio on the speaker. If I go into the Settings -> Connected Devices -> Gear S3 and Disconnect, then the speaker works in Phone. This seems like a bug.