Unexpected `assignment.type.incompatible` when assigning `Integer` in lock checker

I'm working on getting the tests working on jdk11 (#2771) and currently having trouble getting one of the tests for lock to pass. A smaller reproduce of the test case follows. I'm not too sure if this is a bug of the checker or that this means the test needs to be changed.

Command used:
java -jar $checker/checker/dist/checker.jar com.sun.tools.javac.Main -processor lock lock-repro.java

where lock-repro.java is:

import java.util.concurrent.locks.ReentrantLock;
import org.checkerframework.checker.lock.qual.GuardedBy;

class Test {
    final Object lock = new Object();

    Integer dummyInteger(int n) {
        return new Integer(n);
    }

    void integer() {
        @GuardedBy("lock") Integer a;

        a = new Integer(5); // works, no error

        //error: [assignment.type.incompatible] incompatible types in assignment.
        //a = Integer.valueOf(5);
        //                    ^
        //found   : @GuardedBy({}) Integer
        //required: @GuardedBy("this.lock") Integer
        a = Integer.valueOf(5);

        // same error as above
        a = dummyInteger(5);
    }
}

TODO: Update checker/tests/lock/ChapterExamples.java

Start with the provided lock-repro.java example and run the checker command against it, then inspect checker/tests/lock/ChapterExamples.java. Determine whether the incompatible assignment is checker behavior or an outdated test expectation, and update the test or issue behavior so the lock tests pass on JDK 11.