A buyer holding a registered sale deed generally believes the matter is closed. The sub-registrar has accepted the document, stamp duty has been paid, and the deed carries a number. None of that is an adjudication of title.
The sub-registrar registers instruments. He does not investigate whether the executant had anything to convey. A deed executed by a man with no title transfers no title, and it will be registered exactly as cheerfully as one executed by the rightful owner.
This is why the chain matters more than the last link in it. If a partition thirty years ago left a sister's share unaccounted for, her heirs may sue long after you have moved in, and the deed in your hands will not answer them. If a will in the chain required probate and never obtained it, every transfer after it is unsettled.
The practical consequence is that verification has to be done before payment, not before registration. By the time a buyer is at the sub-registrar's office the money has usually gone, and a defect discovered there converts a negotiation into litigation.
What a buyer actually wants is not a deed but a marketable title, and the difference between the two is the whole of this branch of practice.
What clients want to know
How far back should a title search go?
Thirty years is the working standard, or to the first grant where that is later. A shorter search misses exactly the old mortgages and partitions that cause trouble.
Is a bank loan proof of clear title?
No. A bank satisfies itself that the property is adequate security for what it is lending. It does not examine whether you are getting good title, and it will not share its lawyer's report with you.
General commentary on Indian practice, not advice on any particular matter. Law and procedure differ between states and change over time.