When I run the API call for nft/0x4431DDab969B322C62825752388387f0Cd251947 it returns the first 500 tokens, I then run a subsequent call/s to fetch the balance using the offset param, and this seems to retrieve some tokens already fetched in the first/previous call. The number of duplicates in the second/third calls are not consistent.
This process worked perfectly 1 to 2 weeks ago.