Hi Alexander,
I moved To new version 26.5 and here my results:
Please see:
Test data(input/output/QGIS)
5387 Gml Gpx.zip (97.9 KB)
Thanks,...another CRS and you do not re‑project it, the writer discards the...KeepM = false }); // 2. Re‑project to WGS‑84 if needed var sourceCrs...