@Mruther 

To be honest you are using the Deco system outside of the designed specs.  The system is designed to work indoors within 1 building.  They are not really designed to be used in the manner you are using them, relating a signal from the home to a camper. There are just to many factors to accommodate when sending a signal from an indoor unit outdoors to another indoor unit.  Ideally, the best option I see is placing a Deco X50-Outdoor on the back porch to get a better signal to the unit that is in the camper.  Depending on how far the camper is you might even be able to move that unit inside the home and just have the Deco X50-Outdoor provide the signal.  You would just add it to your existing system like any other Deco unit place it outside between the house and camper, where there is a strong signal from another unit and you should be good to go from there.    

  @Mruther 

Oh, I understand completely. The suggestion is based on the red lights on the unit which indicates its lost connection.  This here could also help.  If your hardware version supports this option you would want to have the camper connect the porch unit, instead of the default which is the main unit, unless that unit is completely out of range.  This would help with connection stability and could ensure that drops like that are less likely.  If it doesn't work then maybe consider the Deco X50-outdoor option.

  @Mruther 

Yes, all models of Deco will work with each other.  For the best experience we do recommend that the best featured model is placed as the main unit of the network.  Additionally its worth noting that when running a mixed network, not all features will be available.  For example if you have an M4 and a X20 in the same network the X20's WiFi 6 features will not be available to the devices connected to the m4.