Data connection upon returning to home countries does not work

I am using my Fairphone with 2 SIM cards, one dutch card (Mobile Vikings, KPN NL) and one german card (Simyo, Eplus). I live in Germany and work in Netherlands. Therefore I cross the border at least 2 time every day.
I would like to use the german SIM & german data plan in Germany and the dutch SIM & data plan in Netherlands. For the telephone network this works so far fine, I just use auto connect to network.
For data connection it neither works in Germany nor in Netherlands, I have no internet connection after crossing the border.
When I restart my phone a couple a minutes later, that data connection works, but switching off and on my phone constantly is no option from me, since I use the data for my navigation app. Besides I think it’s quite inconvenient, that I have to manually select/switch the data connection in the settings menu/dropdown.
Does anybody know a workaround or an app that can solve this problem?

Thanks for your help

Not a solution for your problem, but does disabling and enabling the data connection help rather than restarting the whole phone? Or maybe enabling and disabling flight mode? Would save some time if you don’t have to reboot the phone.

Also no solution here, but considering data connection, only one of the SIM cards can do G3 / UMTS at a time. I don’t think there is an option to change this automatically.