Since I have updated to the new Glyphs version 2.6.2 (1268), I have an error message at export:
“The fonts contain glyphs with duplicate production names: f_i, f_idotaccent (f_i).”
I followed the localisation feature for Turkish according your tutorial.
Coming back to the original problem, select f_idotaccent in Font view (Cmd-Opt-1), edit its info (Cmd-Opt-I), and set the production name to e.g. f_i.loclTRK.