Unexpected fees are another reason not to calculate the buffer from the purchase price alone. Before completion, ask for the latest itemised estimate of amounts due and compare it with earlier figures. The exact process and charges depend on the transaction and jurisdiction, but unexplained...
How are you drawing the two neighbourhood boundaries? A few streets can change the mix of condition, size and asking price. I would also separate properties needing work from those ready to occupy. Otherwise the slower condition category may be driving your 62-day result.