Error when making HTTP call in Motoko: Canister http responses were different across replicas, and no consensus was reached

I would have used postman to check response of http post request.
Try hitting url with same post request multiple times and check what actual difference those responses have in there, and then try to process the post request responses inside transform function accordingly to make them same to reach consensus .
For a good example of processing http request responses inside transform function you can refer to

Also if you want to try non replicated http outcalls to avoid transform function for fire n forget type of http requests you can also check :