According to the answers here Why is Buzz the only toy that does not believe he is a toy? a toy starts its existence thinking it is the character it is based on, then it realizes its true nature as a toy and accepts it. We don't know the rest of the process.
In the case of Buzz, I saw this:
Toy Story: he is a new toy, he thinks he is the character he is based on. Then he realizes he is a toy and accepts it.
Toy Story 2 and Toy Story 3: Buzz keeps the skills and the determination of a hero character, he remembers his backstory. I suppose the Buzz Lightyear cartoon is long cancelled in Toy Story 3.
Toy Story 4: Buzz is all doubtful about what to do next, he doesn't behave like an action hero anymore. He even has to ask his recorded quotes for advice.
I can conclude that, given enough time, a toy forgets its origins completely. This didn't happen to Gabby, the Prospector or Jessie because they were exposed to their merchandise or the info in their original boxes.
So, in Toy Story 4, is Buzz Lightyear going through the last phase of a toy's existence when he forgets his origins, like Woody?