JDownloader 2 is free, open-source, and handles PlayerJS better than most paid tools.
"The video downloads but is 0KB / corrupted." Solution: PlayerJS is using encrypted DRM (Widevine). Consumer tools cannot decrypt this. You would need a screen recorder (OBS Studio) as a last resort. playerjs video downloader
It records the stream as it buffers and merges the segments into a single MP4 file. JDownloader 2 is free, open-source, and handles PlayerJS
Free, safe, no viruses. Cons: Requires technical comfort; doesn't work if the video is encrypted (DRM). JDownloader 2 is free