Had the same issue with some of the modules. I bought them on eBay so that might be the reason. As a test I wrapped the faulty module in some tinfoil to discharge all the caps on the board. After that it went back to the original low powerdown current.
I'm leaving the same module on for a few days and see if it comes back. If so I will try to buy new ones from a more official source and see if this makes a difference.