What is the definintion of "problem" in this case? Is it just a rule that you don't like? Or is it something that is fine but doesnt mesh with your table's playstyle? Or is it something that can honestly break the game? And when I say "break" I mean having seen it in action at the table, played the rule in conjunction with the other rules of the game and found that it's not something that can be fixed simply by proper application of the rules as written as a whole.
For me a "problem" is that last thing because then you simply have to house rule it or remove that element from the game.
But just because I make certain changes as to how I play at my table doenst mean that I have problems with the rules. It means, "Hey these rules are fine. But I have something specific that I want to pull of here so I'm going to supplant these rules with my own."
In my case it's more hit points at first level. It's full hit dice + CON score. Not bonus, SCORE. So a fighter with CON 15 starts off with 25 HP at first level. Increases PC survivability and doesnt break the game. Our Campaign has been going on close to 5 years and there's been quite a few character deaths but they've all had fighting chances due to the hp buff.
Does that mean the starting HP rules in the Core Rulebook are broken or a "problem"? Nope. I just like mine better so I use those.