Need Help!- DRO

[OZZIE1952]

I have a milling machine with a 2 axis Sargon DRO.
The display is acting up. When I turn the display on, it suposes to show 0.0000 in both row of LED's. Instead I'm getting random readings or not display at all. Sometimes if I push the clear key and turn it on at the same time it will display correctly. If I get the start up step right the system will work fine.So I know for sure it is not a power supply issue.
There is a Z80 processor on the board and a bunch of other Ic's.
The system was built in 1988. I read somewhere that the problem can be related to the backup battery.
The battery in this case is integrated with sram memory in the same chip. The chip is a M48Z12. What I need to know is if I replace the chip with a new one is there a risk of loosing data that resides in it?. This DRO will save some parameters like a bolt pattern. KenM replied to the same question in a electronic forum saying that if it is a component with a battery built in, I should be able to replace it without the risk of loosing any vital information.
The chip is mounted on a socket.I just want to sure before I pulled it out.
Please help. Thank you.