SSH server add-on won't update?

Hass.io keeps telling me that there’s an update available for the SSH Server (from my current 6.3 to 7.0), but every time I attempt to update, it fails. From the logs:

19-12-07 16:18:24 INFO (SyncWorker_18) [hassio.docker.interface] Update image homeassistant/armv7-addon-ssh:6.3 to homeassistant/armv7-addon-ssh:7.0
19-12-07 16:18:24 INFO (SyncWorker_18) [hassio.docker.interface] Pull image homeassistant/armv7-addon-ssh tag 7.0.
19-12-07 16:18:25 INFO (SyncWorker_18) [hassio.docker.interface] Stop addon_core_ssh application
19-12-07 16:18:26 INFO (SyncWorker_18) [hassio.docker.interface] Clean addon_core_ssh application
19-12-07 16:18:26 ERROR (MainThread) [aiohttp.server] Error handling request
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/docker/api/client.py", line 261, in _raise_for_status
    response.raise_for_status()
  File "/usr/local/lib/python3.7/site-packages/requests/models.py", line 940, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 500 Server Error: Internal Server Error for url: http+docker://localhost/v1.37/images/sha256:52efe0cc0690973eb8787c763a6e4d1155da7015f2bd426c7e9264423253285c/json
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/aiohttp/web_protocol.py", line 418, in start
    resp = await task
  File "/usr/local/lib/python3.7/site-packages/aiohttp/web_app.py", line 458, in _handle
    resp = await handler(request)
  File "/usr/local/lib/python3.7/site-packages/aiohttp/web_middlewares.py", line 119, in impl
    return await handler(request)
  File "/usr/src/hassio/hassio/api/security.py", line 147, in token_validation
    return await handler(request)
  File "/usr/src/hassio/hassio/api/utils.py", line 39, in wrap_api
    answer = await method(api, *args, **kwargs)
  File "/usr/src/hassio/hassio/addons/__init__.py", line 205, in update
    await addon.instance.cleanup()
  File "/usr/src/hassio/hassio/utils/__init__.py", line 29, in wrap_api
    return await method(api, *args, **kwargs)
  File "/usr/local/lib/python3.7/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/src/hassio/hassio/docker/interface.py", line 320, in _cleanup
    for image in self.sys_docker.images.list(name=self.image):
  File "/usr/local/lib/python3.7/site-packages/docker/models/images.py", line 364, in list
    return [self.get(r["Id"]) for r in resp]
  File "/usr/local/lib/python3.7/site-packages/docker/models/images.py", line 364, in <listcomp>
    return [self.get(r["Id"]) for r in resp]
  File "/usr/local/lib/python3.7/site-packages/docker/models/images.py", line 316, in get
    return self.prepare_model(self.client.api.inspect_image(name))
  File "/usr/local/lib/python3.7/site-packages/docker/utils/decorators.py", line 19, in wrapped
    return f(self, resource_id, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/docker/api/image.py", line 246, in inspect_image
    self._get(self._url("/images/{0}/json", image)), True
  File "/usr/local/lib/python3.7/site-packages/docker/api/client.py", line 267, in _result
    self._raise_for_status(response)
  File "/usr/local/lib/python3.7/site-packages/docker/api/client.py", line 263, in _raise_for_status
    raise create_api_error_from_http_exception(e)
  File "/usr/local/lib/python3.7/site-packages/docker/errors.py", line 31, in create_api_error_from_http_exception
    raise cls(e, response=response, explanation=explanation)
docker.errors.APIError: 500 Server Error: Internal Server Error ("readlink /var/lib/docker/overlay2: invalid argument")

Any idea how to correct this? I’ve had to disable auto-updates on this add-on, because otherwise it keeps trying to update itself, failing, and then not re-starting the installed version of the SSH server.

How much spare space do you have on your disk/SD card?

According to df, I’ve got 23.9G free on a 32G card. Seems like that should be plenty of room.