i have not had that issue yet on my iphone 7 IOS 13 updated yesterday evening and have been using this all day with my other ipad. I did have this issue of yours a while back with 12.4.1 and the steps I took to resolve my issue were.
1. go to settings mobile data
2. switch off your personal hotspot.
3. go back to settings mobile data, scroll down untill you see "wifi assist" ( here i have this switched off al the time )
4. turn on hotspot again and this should resolve your issue