Why is this an issue?

There’s no point in chaining multiple OrderBy calls in a LINQ; only the last one will be reflected in the result because each subsequent call completely reorders the list. Thus, calling OrderBy multiple times is a performance issue as well, because all of the sorting will be executed, but only the result of the last sort will be kept.

Instead, use ThenBy for each call after the first.

Noncompliant code example

var x = personList
  .OrderBy(person => person.Age)
  .OrderBy(person => person.Name)  // Noncompliant
  .ToList();  // x is sorted by Name, not sub-sorted

Compliant solution

var x = personList
  .OrderBy(person => person.Age)
  .ThenBy(person => person.Name)
  .ToList();