Clock error on TDS3034


I recently bought a nice TDS3034.
Unfortunately, its clock has a problem: I may set date and time but it does not keep it, not even without a restart.
Could this be just a bad backup battery and if so, could the calibration state be affected, either already or when replacing the battery? Does this model have a Dallas NVRAM?
I’m not at home so I haven’t had time to check amplitude calibration etc. nor opened the case. Fast edge seems ok (have a Leo Bodnar pulser with me).
Thanks for any responses!

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