Attempting to sync with radicale results in "Remote end closed connection without response"

• Vdirsyncer version: version 0.18.1.dev0+g3191886.d20211204
• Server software (and which version): radicale 3.1.7-1
• Python version: 3.10.4
• Operating system: Arch Linux
• Config file: config
• Error output:

Syncing contacts/contacts-3e3ca063-d88c-4cd7-9141-69eb2ca57602
Syncing calendars/calendars-655c997b-5938-499b-9348-e26bbaf26a85
Syncing tasks/tasks-a2e77698-f5c0-4e17-98f1-b16ba78909bd
error: The server returned something vdirsyncer doesn't understand. Error message: InvalidXMLResponse('Invalid XML encountered: no element found: line 1, column 0\nDouble-check the URLs in your config.')
error: While this is most likely a serverside problem, the vdirsyncer devs are generally interested in such bugs. Please report it in the issue tracker at https://github.com/pimutils/vdirsyncer/issues
error: Unknown error occurred for tasks/tasks-a2e77698-f5c0-4e17-98f1-b16ba78909bd: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))
error: Use `-vdebug` to see the full traceback.
error: Unknown error occurred for contacts/contacts-3e3ca063-d88c-4cd7-9141-69eb2ca57602: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))
error: Use `-vdebug` to see the full traceback.
error: 3 out of 6 tasks failed.

• Debug output: debug

Start with the linked config and debug output, then reproduce the sync against Radicale 3.1.7 using the reported Python and vdirsyncer versions. Compare the failing tasks, contacts, and calendars requests with the server response; done means the affected collections sync without the invalid XML or closed-connection errors.