My RV recently blew a hydraulic line while out on a rental. As a precaution I reached out to the next renter to let them know there was a mechanical issue and I wasn't sure if I could get it fixed in time. I cancelled the reservation and used the Mechanical Issue.
I paid quite a bit extra to have a mobile RV tech come out and refab the line and fix the issue. When I went to rebook the RV it was permanently blocked from re-booking for the period of the cancelation.
I reached out to customer support and they could not unblock the calendar. If I had cancelled a month long booking I would not have been able to book my RV on Outdoorsy for the entire period of the cancelled rental. Crazy.
TL:DR; Never use "Mechanical Issues" as a cancellation reason. Customer Support gave me that guidance.