Is it correct to use must have p.p like this?
While they were organizing some papers, they found out that the sensor was meant to work as long as its batteries held out. That meant there must have been wrong with the machine, even though they hadn't noticed this.

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I'm not sure what your question is.
The sentence is wrong - "must have been" is correct, but there is a 'something' missing:
...there must have been something wrong with....
Another example with "must have been": You must have been out when I called.