This is an issue that happens when you have mismatch of type between a Source and Destination table item type.
You should look at the data type in the table for both Source and Destination. You probable have one of these field as nvarchar. If it needs to be nvarchar, that’s fine. If not, simplest way to fix it by changing it to varchar.
If changing it to varchar is not an option, you should open your Source (in my case OLE DB Source).
Right Click and Select Show Advanced Editor.
Select Input And Output Properties tab.
Expand OLE DB Source.
Expand Output Columns.
Select your Column. On the right side you will see DataType under the Data Type Properties group. Change that from “string[DT_STR]” to “Unicode string[DT_WSTR]”
You might have to do the same for the Destination (I am guessing, one of them is already DT_WSTR type.
Hopefully this solves your issue.