More Like This query produced different result after upgrading from 1.7 to 2.2

After Upgrading elastic version 1.7 to version 2.2 we see result as well scoring difference while executing more like this query

For example:

I have 10 docs indexed , search More Like This for doc 1 using version 1.7 returns 8 docs whereas using 2.2 returns 6 docs as well scoring is different