Battery rubbish on second charge

Hello, I bought a Ring doorbell 3 in the Prime day sales and it seems okay so far. The initial charge lasted about 6.5 weeks which seems to be normal (assume Rings estimated battery life is if you pop it in the cupboard for 6 months). But I did the second charge this weekend, up to 100% (reported in app and charge light on battery). 32 hours later I'm down to 72%.... no changes to environment, usage etc... just charged and put back in. Does this sound like a deffective unit? Ring support seems quite difficult to get ahold of so if so I'll just have Amazon send out a new replacement. Edit: It's been 5 or so hours since I posted this and it's now at 60%...... so I'm going to assume I've got a deffective unit and will get Amazon to replace!