You're not the only one to run into this problem, there are several posts in the bugs section. I actually ended up re-rolling my KDF DR because of it, then made the same mistake on my Reman DR. Made a bug report on both, ID #3.369.858, though the ticket does not show up when I look at my tickets.
And the problem seems to be with the Temporal Insight Trait, which is the reward for completing half the story arcs. Once you unlock it with one DR you can claim it as soon as you hit level 10 on any other character, including other DR's. As a result, when you try to claim the reward for completing half the arc on another DR it gets stuck because it sees you already have it.
Which then prevents you from claiming any other rewards, which in turn will prevent you from claiming the Story Arc rewards on your non-DR characters.
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And the problem seems to be with the Temporal Insight Trait, which is the reward for completing half the story arcs. Once you unlock it with one DR you can claim it as soon as you hit level 10 on any other character, including other DR's. As a result, when you try to claim the reward for completing half the arc on another DR it gets stuck because it sees you already have it.
Which then prevents you from claiming any other rewards, which in turn will prevent you from claiming the Story Arc rewards on your non-DR characters.
Just curious ... why 4 ... Rom/KDF & Rom/FED have the same Story Arcs ...