Have similar experience with Maybank.

Here is my guess on why it happen:

I was paying progressive interest during mco (well not actually paying la since Maybank stop auto deduction during 1st moratorium) and even though opr drop, the interest rate for me remain the same... I guess because it is under progressive interest not full release yet.

Now fast forward after got key and start paying full, once the opr revise... then only it change to lower monthly amount.

I guess its their system setting that only able to revise the monthly amount during opr rate change. only that specific time it will reflect.