hat is, if the phone changes between 4g and 5g and wifi connection, so it somehow looses the session or something.
No, because the end-user phone does not access the database. the end-user browsers just talks with your web/app server, and your web/app server communicates with the database , in the internal network. (at least that is what is expected... )

your phone loosing 4g connectivity has nothing to with with database find errors.