Ingestion error while importing data from BIgquery: No user_id or device_id found

Hi everyone,

I have been trying to ingest our Bigquery data to Amplitude. But I have been facing a very weird problem. In some of our tables, We have `anonymous_id`  with a value `anonymous` with string data type and I use this value in place of `user_id` in ingest_config sql query but I get ingestion error with `no user_id or device_id found in the events` whereas in  another table, I do the same with same `anonymous_id` replacing `user_id` but all the data of the table have been successfully ingested into Amplitude. I am not able to understand the difference?

Attaching the ingest_config query here for both the `table1` and `table2` respectively:

SELECT
  event AS event_type,
  STRUCT(event_text as event, event_status_flag as event_status_flag, context_page_url as context_page_url)AS event_properties, -- must be JSON
  UNIX_MILLIS(original_timestamp) AS time, -- event time, must be in milliseconds since epoch (timestamp), e.g. UNIX_MILLIS(timestamp)
  loaded_at, -- Timestamp column required for time based import only, usually server upload time or database insertion time, must be in TIMESTAMP
  anonymous_id as user_id
FROM `vibi-prod.team_monitor_website.download_page_call`

 Query for table 1 with ingestion error and the error is: {"offset":0,"error":"events must have either user_id or device_id or both (Missing device or user id): 

SELECT
  name AS event_type,
  STRUCT(path as page_path,
  url as page_url,
  name as page_name) AS event_properties, -- must be JSON
  UNIX_MILLIS(original_timestamp) AS time, -- event time, must be in milliseconds since epoch (timestamp), e.g. UNIX_MILLIS(timestamp)
  loaded_at, -- Timestamp column required for time based import only, usually server upload time or database insertion time, must be in TIMESTAMP
  anonymous_id as user_id
FROM `vibi-prod.team_monitor_website.pages`

Query for table2 where I get no ingestion error. But what I can guess is in the above `Table1` `anonymous_id` value is `anonymous` wherese in `table2` the value of `anonymous_id` is generated using `uuidv4()` method.

So, my question is, does Amplitude only accepts user_id value is `02c041ca-cf5b-40c0-a214-95bb4b2ebc7f` such format only?