Server error fetching stat var groups for many variables

[Gothmagog]

client = DataCommonsClient(api_key=apikey_datacommons)
county_id = "geoId/06041"
variables = client.observation.fetch_available_statistical_variables(entity_dcids=[county_id])[county_id]
resp = client.node.fetch(node_dcids=variables, expression="->memberOf", all_pages=False)

...fails with:

Status Code: 503
Request URL: https://api.datacommons.org/v2/node
Response: {"message":"upstream connect error or disconnect/reset before headers. reset reason: connection termination","code":503}

However, if I use a subset of the variables, i.e. variables[:2000] as input, it succeeds.

I'm using: datacommons-client[Pandas]