I learned through talking to people from Interval that there are old, tired resorts that don't even show up in searches. Turns out that two of them were in a part of England we wanted to visit. So after much wrangling with the people from Interval, "I assure you, I am not going to ask for my exchange fee back," we were allowed to trade there.
Floors were creaky. Stairs were creaky. Doorways were so short I had to duck. And one place had a mattress was too soft for me. But the staff was great. It was like staying at Fawlty Towers, but in a good way. One place sold beer in their onsite pub at giveaway prices. It was a 5 minute walk to a train station. And it turned out to be one of our better trips.
When I returned, I sent a detailed review to Interval and suggested they not only should remain in the network, they should be taken off search list restrictions. They were clean, comfortable, and in great locations.
I checked this last year and one of the two "double-secret-probation" resorts was still in Interval. As of today, just checked, they're both no longer part of the network. And one is scheduled for demolition.