we have a 2015 cardinal and had the same problem. we cut through the luan wallboard to see what the pullies were anchored to. in our case there was some OSB board in the wall. we bought a piece of steel plate that was larger than the pully plate. we used several larger diameter screws to anchor the steel plate to the OSB. then used self drilling screws to anchor that pully plate to the new steel plate.
in our case the pulley was pulled out because the cables were loose and the cable adjusting blocks interferred with each other. this caused the motor to pull the pullies off the wall.
make sure you adjust those cables properly!!! there a several videos of how to do this on youtube. look for 'how to adjust BAL accuslide cables".
2015 cardinal model 3825fl
2015 dodge ram 3500 dually