For all we know, some bored German submariner sent garbage over the radio as protest; this message was sent two days after Hitler committed suicide, 7 days before VE day. (8 days if you're of the Soviet persuasion) Morale and discipline has a tendency to break down under those circumstances.

Or it could be a transcription error. Modern cryptanalysis tends to be more resilient to transcription errors; one character wrong is gonna be ok, one character inserted/deleted will tend to produce two messages, one with garbage after the insertion/deletion and another with garbage before it. But Enigma messages were...terse, so a half-successful decrypt that gets half garbage and half plaintext might still be recognized by the cryptanalysis algorithm as the wrong key. I expect there would have to be at least two transcription errors to cause both the original German commo to be unable to decrypt it and modern attempts to fail.