World Rally Gaelco words and sprites issue

[makedome]

hello, I'm working on a gaelco world rally that has some grafic issues with words and objects. If someone has worked already on this pcb please can give me some hints to find the ic or the area of the pcb that is possibly broken. Since some rams have been replaced and I see on the other working board that I have that those should be 20 ms, but the replaced ones are 35, could this cause the issue? Also can be something related to suicide battery, even if I measured the voltage and it's around 3v? Thanks