@Gerrell
Just to clarify how the system works, you have two distinct sets of accessories: one set contains the Fish Finder accessories (Sextant, Weather Radio, Fisherman's Pocket Guide) and the Angler Tackle Bag accessories (High Test Fishing Line, Angeler Earring and Tackle Box). These two sets are
independent of each other, so having any Fish Finder accessories does
not impact getting any ATB accessories and vice versa.
Another thing to note is that if you have a completed Fish Finder in your inventory, the "drop only accessories you don't already own" mechanic
stops working for the Fish Finder, and the same applies to the Angler Tackle Box. For example, once you have an ATB, you
can get duplicate High Test Fishing lines.
So the question is, are you getting duplicate Sextants or Weather Radios (and
only those two) while waiting for a Fisherman's Pocket Guide, while
not having a completed Fish Finder in your inventory? Because that
is a bug. Any High Test Fishing Lines, Angler Earrings or Tackle Boxes you are getting are part of a
different set, so getting those is
not a bug.