Geez...I wouldn't buy it until the lien is released. Why would the buyer? And, you would not be able to give clear title which makes it a deal breaker for 99.999% of buyers. I'm sorry this has happened to your sale but the Association (which is the homeowners) will need to make this go away.
If the buyer agrees, if they believe the “5% for a partial release”, you could simply have an agreement where the title company holds the 5% in escrow from your proceeds, with a time limit of say 90 days or so, where if the lien is Not reduced and resolved, the title company releases the 5% to the city for the release. If you Do get lien reduced in that time, pay the reduced amount (your unit’s share) out of the 5%, with you getting back the balance.