Results of SAMPLE clause using a DBlink between 2 Oracle databases not randomised
According to the Oracle documentation for the SELECT ... SAMPLE clause, the sample is random; it is just a coincidence that you are always getting the same rows on the local machine.  You could try adding the SEED(x) clause, where x is a number from 0 to 4294967295; but that may not help going across a database link.

select * from myTable@myDbLink sample(10) seed(42); 


Per the Oracle documentation:


  SEED seed_value Specify this clause to instruct the database to attempt to return the
  same sample from one execution to the next. The seed_value must be an integer
  between 0 and 4294967295. If you omit this clause, then the resulting sample will
  change from one execution to the next.


Notice it is still not guaranteed!