Hi there,
just an observation I made, if you send a query like the following to the GoogleAdsService, the result is reproducibly "Internal error encountered.":
SELECT
customer_client.client_customer
FROM customer_client
LIMIT 1000
The actual limit value doesn't matter, only either adding an ORDER BY or removing the LIMIT clause makes the error go away. Other resources don't seem to be affected by this and as far as I understand the Google Ads Query Language grammar it should be a valid query.