Add know problems section to the docs

doc/developer-center/import-api/guides/07-database-connectors.md

@@ -1176,6 +1176,37 @@ a temporary table. In order to do so, an anonimous dataset will be created in th
 By default an anonymous dataset in the US location will be used if Storage API used; if the data is in a different
 location an error will occur.
 
+
+#### Known Problems
+
+We're still in beta and intently enhancing this connectors, so expect fast changes and improvements,
+but we also have some rough edges at the moment.
+
+##### Project Permissions
+
+If the account used to authorized CARTO (via OAuth) have access to your BigQuery projects but some of the
+[necessary permissions](https://cloud.google.com/bigquery/docs/access-control) to execute the queries in the billing
+query are not granted to the account you won't get any error, but the imported datasets will be empty.
+Please, for the time being make sure you have permissions to admin BigQuery and use its APIS on the billing
+project, and check the imported results if you're in doubt.
+
+The permissions we are aware that can cause this problem (if not granted) are `bigquery.jobs.create` (which allows
+to execute queries in the billing project) and, if Storage API is used,
+`bigquery.readsessions.create` (required to read table data).
+
+##### Column Names
+
+Currently imported data from BigQuery follows a normalization process that adapts the column names
+to [CARTO conventions](https://carto.com/developers/import-api/guides/column-names-normalization/).
+
+This process eliminates uppercase letters and special characters from the column names, which can lead
+to altered and hard to understand names. If this affects you, please assign lowercase names to your
+columns in the imported query (using `sql_query`) like this:
+
+```sql
+SELECT ID AS id, Name AS name, Value as value FROM my_project.my_dataset.my_table
+```
+
 #### Parameters and Usage
 
 To use the BigQuery Connector with the Import API, you must include a `connector` parameter with the following attributes: