See Test.java from the attachment for the reproduction steps:

$ java17 -showversion -cp test.jar -XX:ArchiveClassesAtExit=test.jsa \
  -Djdk.internal.lambda.dumpProxyClasses=DUMP_CLASS_FILES \
  -Xlog:cds Test

$ java17 -showversion -cp test.jar -XX:SharedArchiveFile=test.jsa -Xlog:cds Test
[....]
java version "17" 2021-09-14 LTS
Java(TM) SE Runtime Environment (build 17+35-LTS-2724)
Java HotSpot(TM) 64-Bit Server VM (build 17+35-LTS-2724, mixed mode, sharing)
Exception in thread "main" java.lang.NullPointerException
at java.base/java.util.Optional.ifPresent(Optional.java:178)
at Tester.test(Unknown Source)
at Test.main(Unknown Source)

=========================================
Note that the generated lambd proxy class used "ldc ... Dynamic" for getting a MethodHandle to Base::provideDownstreamSubscription, because the target method is a protected method in a different package. While this method is accessible from Tester (it's from a super type of Tester), it's not accessible from the lambda proxy class.

See here for more info: https://github.com/openjdk/jdk/blob/522b65743ca10fcba0a27d25b8fa11319999e228/src/java.base/share/classes/java/lang/invoke/InnerClassLambdaMetafactory.java#L183-L191

$ find DUMP_CLASS_FILES | grep Tester
DUMP_CLASS_FILES/Tester$$Lambda$1.class
$ javap -c -private 'DUMP_CLASS_FILES/Tester$$Lambda$1.class'
final class Tester$$Lambda$1 implements java.util.function.Consumer {
  private final Tester arg$1;

  private Tester$$Lambda$1(Tester);
    Code:
       0: aload_0
       1: invokespecial #13 // Method java/lang/Object."<init>":()V
       4: aload_0
       5: aload_1
       6: putfield #15 // Field arg$1:LTester;
       9: return

  public void accept(java.lang.Object);
    Code:
       0: ldc #28 // Dynamic #0:_:Ljava/lang/invoke/MethodHandle;
       2: aload_0
       3: getfield #15 // Field arg$1:LTester;
       6: aload_1
       7: checkcast #30 // class java/lang/String
      10: invokevirtual #36 // Method java/lang/invoke/MethodHandle.invokeExact:(LTester;Ljava/lang/String;)V
      13: return
}