I have a federated connection to BigQuery that has GA events tables for each of our projects. I'm trying to query each daily table which contains about 400,000 each day, and load into another table, but I keep seeig this Simba JDBC exception.

I've even chunked out (offset) the query to fetch/append 5000 rows at a time, with a sleep inbetween but I still see this error:

SparkException: Job aborted due to stage failure: Task 0 in stage 2947.0 failed 4 times, most recent failure: Lost task 0.3 in stage 2947.0 (TID 15843) (10.21.40.215 executor 20): java.sql.SQLException: [Simba][JDBC](11380) Null pointer exception. at bigquery.shaded.simba.googlebigquery.googlebigquery.dataengine.BQHTParser.avroStructToString(Unknown Source) at bigquery.shaded.simba.googlebigquery.googlebigquery.dataengine.BQHTParser.avroToString(Unknown Source) at bigquery.shaded.simba.googlebigquery.googlebigquery.dataengine.BQHTParser.avroStructToString(Unknown Source) at bigquery.shaded.simba.googlebigquery.googlebigquery.dataengine.BQHTParser.avroToString(Unknown Source) at bigquery.shaded.simba.googlebigquery.googlebigquery.dataengine.BQHTDataHandler.retrieveData(Unknown Source) at bigquery.shaded.simba.googlebigquery.googlebigquery.dataengine.BQResultSet.getData(Unknown Source) at bigquery.shaded.simba.googlebigquery.jdbcmon.SForwardResultSet.getData(Unknown Source) at bigquery.shaded.simba.googlebigquery.jdbcmon.SForwardResultSet.getString(Unknown Source) at .apache.spark.sql.execution.datasources.jdbc.JdbcUtils$.$anonfun$makeGetter$13(JdbcUtils.scala:484) at .apache.spark.sql.execution.datasources.jdbc.JdbcUtils$.$anonfun$makeGetter$13$adapted(JdbcUtils.scala:482) at .apache.spark.sql.execution.datasources.jdbc.JdbcUtils$$anon$1.getNext(JdbcUtils.scala:376) at .apache.spark.sql.execution.datasources.jdbc.JdbcUtils$$anon$1.getNext(JdbcUtils.scala:357) at .apache.spark.util.NextIterator.hasNext(NextIterator.scala:73) at .apache.spark.InterruptibleIterator.hasNext(InterruptibleIterator.scala:37) at .apache.spark.util.CompletionIterator.hasNext(CompletionIterator.scala:31) at .apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.processNext(Unknown Source) at .apache.spark.sql.execution.BufferedRowIterator.hasNext(BufferedRowIterator.java:43) at .apache.spark.sql.execution.WholeStageCodegenEvaluatorFac...
File <command-6291825545273755>, line 88
 85 df_chunk = df_chunk.withColumn("event_date", lit(event_date))
 87 # Append chunk to Bronze table 
---> 88 df_chunk.write.option("mergeSchema", "true").mode("append").saveAsTable(bronze_table)
 90 offset += BATCH_SIZE