Ok I just found the setting for UA detection in Wordfence.
You find it under plugin setting “Site Performance” below the headline
“You can add items like URLs, cookies and browsers (user-agent) to
exclude from caching”.
Set the following Settings:
If the “User-Agent contains” (without quotes): “Mobile” then do not cache it.
this disables caching for mobile devices. there are also other options you can add.
i hope it help you too.
greeting Marc