There are two scenarios in lexer where the error recovery could be improved:
---
public class BrokenUnicodeEscape {
     private String s = "\uaaa";
}
---

Will produce:
---
/tmp/BrokenUnicodeEscape.java:2: error: illegal unicode escape
     private String s = "\uaaa";
                         ^
/tmp/BrokenUnicodeEscape.java:2: error: unclosed string literal
     private String s = "\uaaa";
                        ^
2 errors
---

But used to produce:
---
/tmp/BrokenUnicodeEscape.java:2: error: illegal unicode escape
     private String s = "\uaaa";
                              ^
1 error
---

Second case:
---
public class UnsupportedTextBlock {
     private String s = """
                        """;
}
---

When compiled with -source 14, the text block is replaced with (ERROR) in the AST, but before it used to contain the text block content (after reporting a proper error).