Some doubt about what?
Jesus had some strong doubt that the four strong apostles could be misled and therefore warned them.
Since Jesus, Himself, proclaimed that St. Peter would come back and bolster his brothers, I don’t think He had any doubts about St. Peter.
Luke 22:31 And the Lord said, Simon, Simon, behold, Satan hath desired to have you, that he may sift you as wheat: 32 But I have prayed for thee, that thy faith fail not: and when thou art converted, strengthen thy brethren.
Nonetheless, what is it that you believe He is warning them about?
Matthew 24 is before the words to Peter about the renegade of Peter,
To Peter he gave an advice to comfort his friends. Only the coming back of Peter was sure.
He warned them not to be misled by false prophets and messiahs within the church that will come for sure.
There’s a certain irony here, given that you were quoting from a JW Bible…
The whole chapter 24 is based on “take care that nobody misleads you” and it is a very serious warning.
You can be sure that the infallible Catholic Church will never mislead you.
Jesus will never mislead me.
Jesus speaks through the Catholic Church.
That’s why He gave you the Catholic Church – so that you’d never be misled!
I’m often reminded to the sad ending to the Book of Judges – “and everyone did what was right in their own sight”. The point isn’t that everyone actually did do right – it was that they followed their own judgment on what that might be. And many were quite mistaken in that judgment.
Jesus didn’t say “ask the apostles or only Peter and they will tell you about it”.
He didn’t say in Matthew 24 to ask the catholic Church because there was no catholic church then.
There were 12 apostles.
One of them was planning to give Jesus in the hands of the priests for money so they had to take care,
Matthew 18:17 New International Version (NIV)
17 If they still refuse to listen, tell it to the church; and if they refuse to listen even to the church, treat them as you would a pagan or a tax collector.
But He said tht you must listen to the Church.
The Church which Jesus Christ established is the Catholic Church. There is no other.