Why is this an issue?

Either use only spaces or only tabs for the indentation of a text block. Mixing white space will lead to a result with irregular indentation.

Noncompliant code example

String textBlock = """
        this is
<tab>text block!
        !!!!
      """;

Compliant solution

String textBlock = """
        this is
        text block!
        !!!!
      """;

Resources