Facetime randomly get loud volumn

iPhone 15 pro, iOS 26.0.1

When talking to someone(iOS is 18.7.1) by Facetime with speaker mode and keep using the phone, sometime it will become so loud even change the volumn to minimun.

Also feel like it's happen when the person I'm calling do something on the phone? open setting or lock phone?

The way is working to fix it is turn speaker off and on again.

Hope it can be fixed.