GPS Recorder stops without reason

Did some hiking yesterday, and yes, the export did seem to stop ~halfway thru.

But: Run the export three times to KML and once to GPX, and the output stopped at four different times: roughly 2140-2150 records. It did not stop at the exact same time / record number.

And something was always wrong with the last record:

KML:

NaN,NaN,NaN
18.95,47.86064,NaN << less significant digits in longitude, my position wasn't at "18.95"
NaN,47.86064,NaN

Last GPX:

      <trkpt lat="47" lon="NaN">
        <ele>NaN</ele>
        <time>2020-03-29T09:46:34.000Z</time>
      </trkpt>

But 2: copy-pasted the App Loader's console output from the browser, did some replace on the raw text, and looks like my whole trip is there, it was transfered by the Bangle, but the culprit is the parsing or export to GPX / KML.
5589 lines, 3 second interval -> some timestamps are missing, start and end timestamp and coordinates seem to be valid.