soundcloud downloads stuck at 33% on firefox in incognito

[mrrreow]

bug description

whenever i try to download anything from soundcloud (doesn't matter if auto or audio mode) with local media processing preferred/forced, my downloads keep getting stuck at 33%

this seems to only happen on firefox-based browsers (tested on firefox and zen) while in incognito, everything works as excepted in a chromium browser (only tested on helium because that's the only one i have on my computer)

reproduction steps

1. open a firefox-based browser in incognito
2. go to https://cobalt.tools
3. download something from soundcloud
4. get your download stuck at 33%

screen recordings

incognito firefox

firefox.incognito.mov

normal firefox

normal.firefox.mov

incognito helium

helium.incognito.mov

links

https://soundcloud.com/bbnomula/nsfw
(also happens with other ones, this is just one example)

platform information

macOS 15.6.1

additional context

i also tested with an unofficial instance out of curiosity, same thing