In all honesty mate I have done exactly what you done tried another AGM battery just to be fully let down Odyssey batteries are the best but need taking care of and never letting them fully discharge no matter what their blurb says they like to be regularly topped up if left for longer then a week or so and not driven they start to swell and collapse
Odyssey make the best AGM batteries that I have used,the problem with a race battery is if you don't drive the car everyday the plates start to lose their charge as no matter what the blurb says about being able to charge from flat numerous times,you need to keep the battery charged up at all-time,They do require more maintenance but they are much more forgiving then a acid battery in the long run,the one that is fitted in my Subaru has been spot on for the last 4 years...
A good battery charger designed for "AGM" batteries is a definite and a cut off switch helps as well.SJ.