SSIS:Truncation may occur due to inserting data from data flow column

I have an SSIS package with a Data Flow that import data from Flat File Source to ADO NET Destination. Output column type of Flat File Source was configured correctly. Input Columns type and External Columns type in ADO NET Destination is automatically generated. But I got below warning messages:

Warning: 0x802092A7 at DFT_import_json, ADO NET Destination Transaction [62]: Truncation may occur due to inserting data from data flow column “reduced_trade_units” with a length of 100 to database column “reduced_trade_units” with a length of 50.

I see the column length of External Columns in ADO NET Destination Input is different with Input Columns length. I manually changed the length to the same as Input Columns length in the Advanced Editor for ADO NET Destination. But It reverted to wrong length again once I closed and open it again. How can I solve it?

After long investigate, I find out it’s related with Destination property setting. By default ADO NET Destination property ValidateExternalMetadata‘s value is true and it will automatically update the external columns type. Need change this property value to false if we wan to manually set external columns type.