I actually had a similar thing happen with a custom race i made, they had saved over 14000 credits by turn 35 and it keep going higher and higher as i was playing. Not sure if its the same but maybe frogboy has fixed it already.
Funny thing as well is they had the Yor tech tree, Yor really don't get any good bonuses to money
. Difficulty was challenging if that matters.
The Ai stuff i gave them was as follows.
1 Growth
2 Tech
3 Fort
4 Dip
5 Wealth
6 Expan
7 Mil
8 Log
9 Inf
And traits was
Opportunistic
scientific
trader
xenophobic