I think you should pull the brake drum off yourself or take it to a different RV repair shop for an inspection. Here is a photo of our left rear brake shoes on our previous Winnebago 2101DS. Note: the front shoe is the short shoe. You definitely need the brakes inspected. On our current trailer using the Tekonsha P3 brake controller the setting is 5.5 and we have very good braking. I know the instructions talk about testing to lockup but I never increase the setting that much because you can flat spot a tire and ruin it. I only increase the setting until I have adequate braking.
