I checked contents of provided *.FIT files (
from Sibstr post). Route data indeed looks normal with much longer than >167km actual distance, but for some reason distance accumulation is capped at ~167 km (167768.33 meters for files 1 & 2 and 167766.73 for file 3). These distances are very close (slightly smaller) than 2^24/100 = 167772.16, that's very suspicious.
Wrong distances are both in a .FIT summary data and in raw record data, thus it's showed everywhere wrong (on eTrex SE or any programs that can open *.FIT files).
Sibstr eTrex SE had SW version 4.20. I used 3.10 version for longer trips (>1400 km), but the distances were accumulated and showed properly for me. I will have to check if I have long trips with 4.20 recorded.
The only few things I see different are a) minor setup difference (Czech vs English, metric vs statute), b) sport set as driving vs hiking. These things are very minor and should not affect calculations, but that is worth checking just to be sure.
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