Why does ChatGPT act like he can't do while he definitely can?

I am just confused…
To extract certain part of the data from txt file (since its not organized), I am asking GPT to read my txt file and paste word-for-word my content…but

lol, he was able to do it perfectly for several times past 3 minute and then…GPT is like “aww… I don’t think I can paste you words. I am not able to do that sorry…”

It’s like asking Harvard math professor to solve 1-digit addition problems and after solving 99 problems, he goes to the last prolem: “1+1” and saying “I can’t”

chatGPT these days are getting more and more dumb I think…I bet free version will do the same job lol

Why is he acting like he can’t do it — and he needs my encouragement to receive the “buff” and try doing it — which in the end, proves he could do it…WHY???