Forum auto-banned me from replying to original thread because @James never answered and users are not allowed to reply to themselves.
Tried, and it didn’t work.
Two weeks have elapsed since I told you this, and still you’ve provided no response. 
Meanwhile, I note Infuse’s “Sort by Filename” setting also breaks TMDB Collections sorting, perhaps providing insight into why “Sort by Filename” for TV items doesn’t actually sort by filename as you recently assured me it would. I hope this insight helps you fix the problem(s).
Consider:
I suspect Infuse treats TMDB’s Collection titles as defacto ‘filenames’ for the collected grouping when “Sort by Filename” is set.
TMDB’s “The Vampire Chronicles” collection, when sorted by Title, is correctly alphabetized under “V” for “Vampire” — because “Sort by Title” correctly ignores the leading article “The ” when present in such titles.
(*) Infuse does NOT correctly ignore the other English language leading articles “A ” and “An ” — an inexplicable discrepancy that needs to be fixed immediately — nor any common foreign language equivalents such as “Das ”, “Die ”, “El ”, “Ja ”, “La ”, “Les ”, or “Los ” when sorting by title — anywhere in the app.
…
When Infuse is switched to ‘Sort by Filename’, Infuse correctly stops ignoring the leading article “The ” when present in users’ video filenames. Similarly, Infuse stops ignoring them when they are present in TMDB Collections titles (here treated by Infuse as defacto filenames).
All TMDB Collections whose titles begin with “The ” are now incorrectly alphabetized under “T” (for “The”) regardless the titles or filenames of the films contained within. This is obviously undesirable behavior.
It is clear Infuse is not looking beyond the TMDB collection’s title because the titles of the films in the “The Vampire Chronicles Collection” are “Interview with the Vampire” and “Queen of the Damned”. Neither begins with “Vampire” and neither would otherwise be alphabetized under “V” — nor incorrectly alphabetized under “T” since neither films’ titles begin with “The ”, either.
So why is Infuse (set to “Sort by Filename”) sorting my TV Series “The Expanse” under “T” (for “The”) when neither the containing folder (named “Expanse ,The (2015) …”) nor any episodes (each named in the pattern “Expanse (2015) — SxxExx …”) begin with “The ”?
I suspect because Infuse is simply (and lazily) treating the TMDB Series Title (“The Expanse”) as a defacto filename — just as it does for TMDB Collection titles.
@James, do not despair, because I also offer you a solution.
In both cases where you decided to treat TMDB TITLES as defacto filenames because actually analyzing users’ actual filenames was too unwieldy or difficult; do this: Alphabetize them as you would Titles.
For TMDB Collections, this would result in what users likely want, anyway. Users can’t edit TMDB collections so we already have no control on how they are organized. Keep them organized by title no matter the setting in Infuse.
For TV Series, which users OUGHT to be able to rename as they see fit to control how they are sorted (just as they presently can with movies), preferably do this: treat the parent folder name (the name of the folder containing the season subfolders — or if the latter are not used, the name of the folder containing all the TV Series’ episodes’ video files — as the defacto filename for the entire “collection” of video and metadata files for each given series.
Otherwise, if you can’t figure out how to program Infuse to accept anything but TMDB’s title as the defacto sort name for everything that makes up a TV series, then also alphabetize that TMDB title as Infuse alphabetized titles — no matter the user selecting “sort by title” or “sort by filename”.
And finally — please —
Add leading “A ”s and “An ”s to the ignore lists!
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