In one of my previous post, I explained about the navigation property naming issue when working with Lookup fields using the WebAPI endpoint in “CDS/CRM Connection Manager”. Recently, I got a mail from Kingsway Soft support team with a Hotfix to resolve this issue. I installed this Hotfix in my machine and ran a simple package successfully to update custom lookup (account) on Contact entity.
This Hotfix is part of the most recent official release (20.1.0.1564). You can download this from the below link.
https://www.kingswaysoft.com/products/ssis-integration-toolkit-for-microsoft-dynamics-365/download
So, I would recommend everyone to use WebAPI endpoint instead of SOAP in “CDS/CRM Connection Manager” due to the fact that SOAP endpoint is deprecated and no longer supported by Microsoft.
You can find all enhancements of the recent official release (20.1.0.1564) in the below link
https://www.kingswaysoft.com/products/ssis-integration-toolkit-for-microsoft-dynamics-365/change-log
Happy migration….
Phani Rajasekhar 
I’m still receiving the same error even with the latest version of the Kingsway Toolkit.
I am still getting this error, using V21.1 KinswaySoft version