Weighted round robin dns between 2 Cloudfront distributions

We are trying to use aws to do some a gradual deployment test with our javascript code, but it seems to fail us

we created 2 S3 buckets with CF distributions :

a.example.net -> aaa.cloudfront.net

b.example.net -> bbb.cloudfront.net

than we created a weighted round robin DNS entry in route53

test.example.net -> (cname) -> aaa.cloudfront.net (5)

test.example.net -> (cname) -> bbb.cloudfront.net (95)

in the S3 bucket we put a file with the CF corresponding domain name for each bucket :

http://ift.tt/1crudSt

What I am expecting is to get 95% of the time bbb and 5% of the time d3nrwpaeicu4xy. What we actually get is aaa 100% of the time :(

I opened a ticket to the route53 team to check if this is a problem with the dns configuration but they have shown me , and I have seen it myself that the dns queries split between the 2 buckets.

Hope this is clear enough.