"charset: error getting wide character buffer size" – UTF-8 / UNICODE *bug* in [text] ?

dear all,
have posted this on the max facebook-group and also written cycling a mail – would be super gracious if anyone could point me in any direction.

i'm currently working on a librarian for a synth / euro-rack module. therefore, i'd like my patch to download and parse a text-file from the developer's webpage http://endorphin.es/cargo3/constants.js

the file is downloaded via [jit.uldl], then stored to disk, then read into a [text]-object from where it's dumped.

on macOS 10.12.6, this works just fine.
on windows (8 + 10), i get a "charset: error getting wide character buffer size" when ever reading the file into the [text]-object... opening the file in a texteditor on windows, storing at as UTF-8 and then loading this new file works, how ever.

any clue?