Linking an authority to a subject field (65X mostly) copies the value "7" as second indicator. According to the MARC 21 Format for Bibliographic Data (http://www.loc.gov/marc/bibliographic/bd650.html) second indicator = 7 means that the source of the subject heading is recorded in subfield $2 (in coded form). That means that every time a cataloger links an authority record he or she has to change this indicator or to add the applicable code in subfield $2.
I cannot reproduce this problem in master.