Amiga 1200 losing time

[Drummerboy]

My old Amiga 1200 is occasionally losing time. I replaced the RTC battery about a year ago so this shouldn't be the problem. When it first happened it lost a few hours, but most recently it went back to June 1996! As I say this has only happened twice in the last few weeks. The RTC is part of a Hawk RAM expansion board. I've left the Amiga switched off since Tuesday afternoon and will switch on again tomorrow morning (roughly 36 hours down time) to see if the problem happens again. I will probably change the battery just in case this is the cause. Could there be anything else causing this problem?
 
Thanks.
 
Nemo

Check if the Battery contacts are whether he is making good contact