Just for grins, I decided to look up how the expression same old, same old was translated into German in the dubbed versions of two Seinfeld episodes.
The first was S5 Ep16, The Stand-In, at ~2 min:
[Kramer and Mickey enter]
—JERRY: Hey! Hey Mick.
—MICKEY: Hey Jerry.
—KRAMER: What's doing?
—JERRY: Nothing, what's doing with you?
—KRAMER: Same old, same old.
In the audio of the dubbed version, the last line was Immer dasselbe. The UT had Immer das Gleiche.
The second instance was in S9 Ep22, The Finale Pt1, at ~7 min:
[Jerry and George are escorted into the office of Mr. Kimbrough, the new president of NBC]
—KIMBROUGH: Anyway, let me tell you why I called. When I took over here last month, I reviewed what was in development,and it was pretty much same old, same old.
—GEORGE: Been there, done that.
—KIMBROUGH: Right. I was looking for something different. Something that would have people talking at the water coolers.
In the dubbed version the audio of his line was Das war alles dieselbe alte Masche, and the UT had Alles nicht so aufregend.
I have three observations
1. The subtitles in the English version are extremely close to what was actually said, but in the German version there is little correspondence. I watched the full episodes and eventually just turned off the German UTs because the mismatch was too distracting.
2. Both of the examples seem to me to more closely match the Merriam-Webster definition: used to refer to something that has not changed . Maybe there is an AE/BE difference, or maybe a generational one, but the annoying and boring aspect emphasized in the Cambridge definition seems a bit foreign to me.
3. The Kramer example highlights a use of the phrase same old, same old that more closely matches my experience. Its often just a pat reply to questions such as how's it going?, how are you doing?, how was work today?, how was your trip? It's a fixed phrase that doesn't mean much of anything. The person answering views the question as routine and not a real request for details. I still wonder whether alles wie gehabt would be the best equivalent of that use.