java_lang_String class methods have assertions like:
assert(oopDesc::equals_raw(value, java_lang_String::value(java_string))
The naked oop comparison can fail if value moved for GC like Shenandoah, should use
assert(oopDesc::equals(value, java_lang_String::value(java_string)) instead.

The raw equal comparisons were introduced in JDK-8217442, but only manifested after JDK-8213229, because references in stringtable are not longer updated at safepoints after JDK-8213229.