Does the server crash or only the app?

I had issues on my phone, jellyfin app would crash on certain media files. But when viewed in a webbrowser it worked without issues. My mom was also able to play the same file on her phone .. In my case it was my phone operating system (crdroid). A future update resolved it.

From the servers point of view i just stopped watching so no error log was created. If you can watch the same media in a webbrowser, your phones/tvs os is to blame.