We have the electric drum brakes that were standard in 2006 so no problems. Since yours is a 2008, you should have the electric over hydraulic disk brakes. The symptoms you describe are common with the disk brake system and 2008 ford trucks. The fix is a special controller that is added to the trailer brakes to make them work properly with the Ford integrated controller. I would suggest calling DRV with your unit number and ashing them which controller you need (probably a Carlyle). We store our rig inside so do no use a cover. Have tried them in the past and could never find one that stands up to the winds we get during the winter. They always seem to rub through on the corners and take constant checking to make sure they do not loosen up and slide off.
Rick and Janice Binns
2006 MS 32TK3, Mor/Ryde Pin Box and I.S., Auto Level-Up
2012 Ford F450 6.7 L Diesel, air bags and 25K Reese Signature hitch (factory installed)