Chad Callihan enables a trace flag:
In SQL Server 2016 and 2017, trace flag 460 can be used to gather additional details about string truncation errors. You may be familiar with the “String or binary data would be truncated” error message. Have you been left wondering what would be truncated? This is where trace flag 460 comes in. When enabled, the error message will include details on where exactly the potential truncation is taking place.
Read on to see if this is something you might benefit from enabling.