A close second is a rental or short-term stay restriction the buyer did not know about until after they had already planned to use the unit that way, a restriction that can also affect whether CMHC or another mortgage insurer will approve financing on that specific unit. Condo corporation bylaws can restrict or ban rentals entirely, and that detail sits in a document most buyers never read closely.
Financing can also stall a purchase when a lender will not approve a mortgage on a specific unit because too high a share of the building is rented out or the reserve fund fails its own review, a risk a buyer's own home inspection, typically $400 to $600, does not catch because it only looks at the unit itself.
All three problems live in paperwork the listing photos never show. Get your hand-reviewed valuation from Joel Dyck.