The Papacy is only an office, it is not a Sacrament. When one accepts the office, one acquires all of the authority that comes with it, including the ability to teach infallibly on matters of Faith and Morals. If one relinquishes the office, the authority goes to the next bishop who accepts the office. The Holy Spirit will never be confused about who rightly holds the office.
This is highly unusual to be sure, but not unprecedented. Things regarding the “end of days” seem to be happening with more frequency. If the next bishop to take the Chair of Peter has “Peter” as a first or last name, or as his papal name, we will all be wondering if St. Malachy’s prophecy is complete.
A pope resigning the office is highly unusual but not unprecedented.
A pope resigning the office BECAUSE of advanced age or because he is physically weak IS unprecedented, and has NEVER been done in the 2000 year history of the papacy. I will repeat a third time: Popes is far worse physical condition than Benedict, and older, continued to reign.
If you disagree with my argument, show we any example in the last two millennium where a Pope "retired" because of his age of physical strength.