I have the same problem, also running the video data from a Mac with Big Sur. The videos can be accessed and displayed through my network via another computer but on the my Raspberry 2 with LibreELEC 9.2.6 they do not start. It seems to start playing the video first but then aborts instantly. Checked with different videos/formats. Would be really thankful for a solution. Worked fine with my older Mac and Openelec before...