Multisport FIT file rejected as "invalid" by Garmin Connect (unknown_233 message type)

Hi all,

I recorded a multisport activity (run-bike-run duathlon) on my Forerunner
965 on 2026-08-23. Garmin Connect rejects the file as "invalid" via all
import paths (auto-sync, Garmin Express, manual web import).

Inspecting the file with a third-party FIT tool shows it's complete and
readable (7,394 messages, 1,561 record entries, 11 laps, all sessions
present). It contains an unofficial/undocumented message type
(unknown_233, 2,632 occurrences) that isn't in the official FIT SDK
profile — possibly what's tripping Connect's server-side validator.

Has anyone seen this before, or is there someone here who could take a
look with FFRT (Fit File Repair Tool)?

Device: Forerunner 965rennen.zip
File attached.

Thanks!

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