It's crazy how this isn't simple. Surely all they have to do is to tally up the debts secured by the apartment, then sell the apartment and use the money to pay as much of the debts as possible. Any remaining debt is the lender's loss, that's the risk they take when giving out loans.

If any debt does need to be tied to the apartment rather than the person, then it simply needs to be registered in a publicly (easily) accessible way. If someone fails to register their debt in a timely manner then it should be forfeit. It should be registered at the time it takes effect. Lender should be responsible for making sure the registration is complete before giving out the debt, if someone takes out a loan then sells it before the debt has been registered that's the lender's problem. They can't retroactively add a lien to my property because the previous owner took a loan when it was their property. That's not reasonable. If the lien is not registered then it doesn't exist, it should be that simple.

I feel like any statement with "surely all they have to do" is going to miss some nuance.

In this particular case the apartment is owned by the coop (that's how coops work) and the mortgage is for the shares in the coop. So maybe more complex than a basic foreclosure where it might possibly work more like you'd think.

I think the broader point is if real estate is selling well below what is you would expect, there's a reason for that.