Why bother?
I am not a fan of attached RV ladders. Most are too weak to hold a plus sized guy like me. Plus, you have one access point to your roof no matter where you need to go. Walking all over your roof is not recommended. As you posted, they are expensive to repair or replace.
I use a collapsible ladder. I installed hooks so it sits on my back bumper in transit. its one of those that doubles as a step ladder . If you watch RVs traveling down the road, a ladder is the most common thing attached to the RV ladder.
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