Are all the notes in the same voice?
Could you upload these two bars of your project?
May be because the chord consists of two seconds.
You can flip the second and third tie, but the result will not best.
It seems to be caused by the large distance between the two chords. Since ties extend horizontally, their curvature increases.
You can reduce that value (maybe not a good idea since it’s a global option):
Or arrange them differently in Engrave Mode:
Or adjust them manually.
Interestingly, this option has no effect, I’m not sure why.
Yes Charles. But change note spacing may affect the music above (which isn’t visible in the screenshot), which may contain thousands of demisemiquavers. 
Of course, I only used NSC to reproduce this huge spacing in an empty project!
I understood perfectly well, dear Charles; I was just having a bit of fun with my demisemiquavers.
Of all the solutions you’ve suggested, manual adjustment in Engraving mode seems to me to be the best. Dorico can’t be perfect at everything first time round, and sometimes you just have to roll up your sleeves a bit, don’t you think?
Interesting, thank you.
Indeed: