Nobody wrote down who owns it

What actually happens

A founder invents before the company exists. A consultant writes the algorithm. A student does the experiment during a sponsored project. An intern builds the prototype. In each case the invention was devised by a natural person, and unless there is a written assignment - or a clear contractual obligation to assign, properly executed - the company's title is at best arguable.

Indian law requires assignments of patent rights to be in writing, and requires them to be recorded in the register to be effective as evidence of title. Neither of those things happens by accident.

Where it surfaces

It surfaces in a data room. An investor's counsel asks for the assignment from each named inventor, and there is not one. Or there is one, signed after the founder had already left, or signed by someone who was never actually an inventor.

The consequences range from a delayed closing to a re-priced round to an indemnity that sits on the founders personally. In litigation it is worse: a defendant will attack title before attacking validity, because it is cheaper.

What a clean position looks like

Every named inventor has signed a written assignment covering the specific application, executed before or at filing, with the correct legal names. Employment agreements contain a present assignment of inventions, not merely a promise to assign in future. Consultants and contractors have equivalent clauses. Sponsored research agreements say explicitly who owns what, and whether the sponsor gets a licence or the title. Assignments are recorded with the Patent Office.

Inventorship is revisited when the claims change during prosecution, because inventorship follows the claims.