It would seem that age is catching up with me!! help

So I have this Vodavi Starplus DHS system in my office.

Yes, it has multiple gray whiskers but, it still operates as it has been
for maybe the past 25 years or so.
Well it has been except for the past 2 days.

Go to make a call on Line 1. Press the button and dead air. Checked
the other two lines and again dead air. However, when dialing the
numbers from my cell all phones ring for the incoming call. However,
when answering the call you get dead air. call

Pressing any extension number works internally as it should.

Presently the quick fix is to power cycle the system.
Then all goes back to normal and all works as it should.
This has now happened two times. Once yesterday and once today.

Looking at the mother board the battery shows corrosion on the one end.
Which is not surprising giving the age. But would a bad battery cause the
condition described above??

My first concerns would be that if I replace the battery, will I lose all programming??

The second concern would be is the battery what is causing the problem. If it is
not then any effort spent replacing the battery would be a waste of time.

Does anyone have some thoughts on the what might cause the above to happen??

Thanks for any hints.

Les