The short answer
Late discoveries leave little time to resolve problems, leading buyers, sellers, or lenders to walk away.
The closer to exchange a problem is found, the fewer options everyone has to fix it. What might have been a manageable issue with weeks to address it becomes a reason to abandon the whole transaction with days left.
Why this matters for your purchase
This is the kind of thing a PropM8 Property Intelligence Report is built to surface early, before solicitors, surveyors or lenders are involved, while it still costs nothing to walk away.