If you just want peace of mind then call cc and set all billing date to same. If it's ltf card keep it somewhere just to bring it up during offers else if it's paid see if you really need it.
The easiest card to hit milestone is HDFC money back plus
It comes in rupay varient so can use it for upi
Just need to hit 50k per quarter to get 500 rs voucher.
I heard that banks can only afford to give discount as much as 5% flat to exclusive 10% only because of emi and late payment with interest. MDR mostly break even for them.
There could be multiple reasons for it going from missing the due date, entering the wrong due amount, delay by app or website, delay from the bank to accept your payment, receiving a statement late to having no money to pay. I hope you would like to share your experience so that we can learn...