You’re running Nextcloud as a Snap package behind Cloudflare, which is known to cause issues with large file uploads—especially when both layers apply their own limitations or buffering policies.
I’ve dealt with similar problems and shared my findings here:
Nextcloud app error when uploading (Snap + Cloudflare context)
From my experience and testing, the combination of Snap packaging and Cloudflare proxying is one of the worst setups if you plan to upload or sync files over 1 GB reliably:
- Cloudflare, unless you’re on a paid plan, enforces a hard 100 MB upload limit (over proxy).
- Debugging is harder due to abstraction on both ends.
If you’re serious about uploading large (video) files, I’d strongly recommend moving to a standard installation. Personally, I’ve tested Nextcloud AIO (non-SNAP) behind Nginx Proxy Manager, and it handles large file syncing without issues:
Testing large file synchronization with Nextcloud AIO and Nginx Proxy
You’ll get full control over PHP settings, proxy behavior, disk I/O tuning, and memory handling. On that stack, I’ve uploaded and synced files over 20 GB without a single crash or failure.