This Is When Ron Isn't Talking To Harry In GOF And Harry Doesn't Understand Him.

The books are centred around Harry and we don't get much insight into either Ron or Hermione's inner struggles. But we get insights into Ron's character four times and 3 of them are from Hermione's perspective

This is when Ron isn't talking to Harry in GOF and Harry doesn't understand him.

“Look,” said Hermione patiently, “it’s always you who gets all the attention, you know it is. I know it’s not your fault,” she added quickly, seeing Harry open his mouth furiously. “I know you don’t ask for it…but - well - you know, Ron’s got all those brothers to compete against at home, and you’re his best friend, and you’re really famous - he’s always shunted to one side whenever people see you, and he puts up with it, and he never mentions it, but I suppose this is just one time too many…(GOF)

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This is when the twins leave the school

“You know,” said Hermione, as she and Harry walked down to the pitch a little later in the midst of a very excitable crowd, “I think Ron might do better without Fred and George around. They never exactly gave him a lot of confidence.” (OOTP)

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This is when Ron is wearing the locket and the argument is going on between him and Harry at the tent

“Take off the locket, Ron,” Hermione said, her voice unusually high. “Please take it off. You wouldn’t be talking like this if you hadn’t been wearing it all day.”

“Yeah, he would,” said Harry, who did not want excuses made for Ron (DH)

Look here. Harry doesn't understand him even one bit. But Hermione does. She knows he wouldn't have acted that way it werent for the locket.

And ofcourse the 4th one where Ron deals with the locket and destroys it.