Weird problem with curry sauce
I think the times you did it with no troubles you used smaller portions, right? These big portions simply do not cool down quickly enough, and the temperature stays too long in the danger zone, say between thirty and sixty celsius. Bacteria grow very quickly around these temps, and so they spoiled your curries. Their waste is lactic acid or alcohol and carbondioxide, and that were the bubbles and the smell. You solve it by cooling down rapidly, so in smaller portions. The other option is that it stayed too long in the danger zone on the buffet, it was the last to go. Probably both... buffets are dangerous in the best of circumstances...in that case you also have to serve smaller portions on the buffet next time.