distributed transaction performances after migrating from 11g to 19c

Ciao

After upgrading two 11g databases to 19c ( with expdp/impdp and new statistics calculated with dbms_stats ) 

many queries using dblinks between the two database decreased their perfromances

queries using objects on both database works slowly

queries working on remote node only ( via dblink ) have a different behaviour and performances look good

query I used to test is accessing two joined remote tables and a local function which is a part of a package 

in 19c it seems the join between remote tables is done on local database while using 11g on remote one which is faster

i tried to exclude local function and it works fine also in 19c environment ( join is executed on remote )