On an upgraded V12.0.1 site I'm getting the following error at the end of an "Export Everything":-
Error: Could not load type 'Umbraco.Forms.Core.Interfaces.IFieldPreValueSource' from assembly 'Umbraco.Forms.Core, Version=12.0.0.0, Culture=neutral, PublicKeyToken=null'.
Using uSync 12.0.2 & uSyn.FormsEdition 10.0.1.0 & Umbraco.Forms 12.0.0
Any advice appreciated.