wi-fiが遅い人
https://sumahoinfo.com/xperia-android-8-0-7-1-xz1-xz-premium-xz-wifi-disconnect-issue-may-be-caused-by-router-wep-setting

簡単な対処法
https://youtu.be/0ohF2eVW7QM

Googleの対応
https://sumahoinfo.com/google-play-service-confirmed-to-be-the-caused-of-android-wifi-disconnect-issue-fix-coming-soon