Python to construct CASE WHEN update SQL statement

I try to update 2K rows in BQ

def update_bq_ads_status_failed(self, update_ads):
    affected_rows = 0
    for update_ads_chunk in split(update_ads, _UPDATE_CHUNK_SIZE):
        ad_ids = [item["ad_id"] for item in update_ads_chunk]
        removal_errors = [item["removal_error"] for item in update_ads_chunk]

        update_removal_error = ""
        for ad_id, removal_error in zip(ad_ids, removal_errors):
            update_removal_error = update_removal_error + \
                                   f''' WHEN ad_id = '{ad_id}' Then '{removal_error}' '''
        affected_rows += self.update_bq_ads_status(f"""
                        UPDATE '{table_full_name}' 
                        SET status = 'Failed Removing'  
            SET removal_error = CASE {update_removal_error} END 
            WHERE ad_id IN {str(ad_ids)}
            """)
    return affected_rows

I'm getting this error. I know it's too vague and not possible to debug like this.

timeout=300.0, headers={'X-Server-Timeout': '300.0', 'Accept-Encoding': 'gzip', 'Content-Type': 'application/json', 'X-Goog-API-Client': 'gl-python/3.8.10 grpc/1.39.0 gax/2.0.0 gapic/2.26.0 gccl/2.26.0', 'User-Agent': 'gl-python/3.8.10 grpc/1.39.0 gax/2.0.0 gapic/2.26.0 gccl/2.26.0'})), last exception: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

I'm trying to eliminate errors. Is my BQ update syntactically correct?

What's the BQ update timeout?

Several issues with last UPDATE statement:

• Avoid quoting identifiers like table names (unless GBQ allows its)
• SET should be used once with comma separation for multiple columns
• Square brackets are interpolated in WHERE condition which requires parentheses

Consider adjusted code:

update_removal_error = " ".join(
    f"WHEN ad_id = '{ad_id}' THEN '{removal_error}'"
    for ad_id, removal_error in zip(ad_ids, removal_errors)
)

affected_rows += self.update_bq_ads_status(f"""
    UPDATE {table_full_name}
    SET status = 'Failed Removing'  
      , removal_error = CASE {update_removal_error} END 
     WHERE ad_id IN {tuple(ad_ids)}
""")