A buyer is concerned about a property where the original owner's mortgage (MOD) charge was cancelled four years after the flat was sold to the current seller. Although the original owner's loans were cleared before the sale, the MOD cancellation and a new charge in the seller's name only occurred much later. The buyer is worried this could indicate foul play or a genuine banking error and is seeking advice on whether to proceed with the purchase, suggesting precautions like newspaper ads and obtaining a 30-year EC.