@Volker  Make sure that you also enable schema evolution in your write stream operation. You can do this by adding the mergeSchema option when writing to the silver table. This allows the destination table to automatically adapt to the new schema.

silver_df.writeStream \
    .format("delta") \
    .option("mergeSchema", "true") \
    .option("checkpointLocation", checkpoint_path) \
    .outputMode("append") \
    .table("silver_table")