- be careful with backing up to WebDAV unless it’s your own webdav backend that you can adjust / debug. Murena fronts their php with nginx and there’s a risk of things not to work, see the 0-byte issue: How to configure DAVx5 for file access? - #14 by tcecyk
- I’d try a device-local backup first until successful, transfer that folder with Seedvault or RoundSync