My perspective on estoppels is somewhat jaded and definitely colored by a recent experience.
My title company asked for, and received, an estoppel for a contract I was buying, and did not note any issues. Working from the belief that Wyndham would not transfer anything that had a balance on it, they went forward and processed the deed. Once it was in my name, I found out - long after the fact, since there is nowhere to see it online - that the contract transferred with over $2300 of back maintenance fees, over $400 of collections fees, and various late fees and billing fees totaling over $2800.
Needless to say the title company is working hard to get the seller to get this straightened out.
So what happened? The assumption that Wyndham won't transfer a contract that has outstanding maintenance fees due on it is WRONG. In fact, they will transfer it, even if it's coming from a flagged or suspended account, and they will do so regardless of what is in a third party purchase agreement. The onus is on the BUYER and their title/closing company to ensure that there is no balance or back maintenance fees due.
One might think I'm advocating for the estoppel, and to an extent I am, but the estoppel is just a snapshot in time. If the fees are current as of July, that does not provide any guarantee that if the contract actually transfers in November, that any of those fees will have been paid in the interim, regardless of what your purchase agreement may state.
This is one of the reasons I don't like ebay sellers that insist on using their own captive closing company (and most of them do). In that situation, the closing company is representing the seller...