Tektronix 2245A oscilloscope - battery problem, or not.

[tubeamptech]

Hello,
I have a Tektronix 2245A oscilloscope, which I use in my repair shop. Back in 2007, I lost the signal trace, and the LED's went out. Found out the back up battery had died, I replaced it, and everything has been fine until now. Now I have the same symptom, so I put a new battery in, a Panasonic 3V, BR2/3A. I fired it up, it went through the self cal routine, and at the end it reported a possible battery failure. Does anyone have any idea's as to why that would be? The old battery, and the new battery are all measuring above 3 V. I thought I would change it, just in case the original had lost capacity. The only thing I can think is I have a connection problem somewhere, or there is a cap that's gone bad or leaky in the battery circuit.