I have a quite a bit of complex project. I am using structs inside another struct as an array and after modifying any variable things get really nasty. Tons of error about Unknown struct and also this warnings:
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'StructProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:GridPosition', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'ObjectProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:inventory_ref', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'StructProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:Stat', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'StructProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:GridPosition', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'ObjectProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:inventory_ref', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'StructProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:Stat', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'StructProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:GridPosition', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'ObjectProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:inventory_ref', MetaData 'False', Flag 'True'
LogBlueprint:Warning: ExposeOnSpawn ambiguity. Property 'StructProperty /Engine/Transient.REINST_Inventory_Item_base_C_6:Stat', MetaData 'False', Flag 'True'
Warning: ImportText (StatID_6_8722CFDC45B1D1F05B1E579647D8BC8A): Missing opening parenthesis: "",Stat_5_32975BDC42BA5A9EF33E269F3491081E=(RemainingHealth_6_B558455141B171C597642CB408C084CE=0,Enchantment_10_EF43AA5C4B223B705D884DA1FDB9D26D=))
Warning: ImportText (StatID_6_8722CFDC45B1D1F05B1E579647D8BC8A): Missing opening parenthesis: "",Stat_5_32975BDC42BA5A9EF33E269F3491081E=(RemainingHealth_6_B558455141B171C597642CB408C084CE=0,Enchantment_10_EF43AA5C4B223B705D884DA1FDB9D26D=))
Warning: ImportText (StatID_6_8722CFDC45B1D1F05B1E579647D8BC8A): Missing opening parenthesis: "",Stat_5_32975BDC42BA5A9EF33E269F3491081E=(RemainingHealth_6_B558455141B171C597642CB408C084CE=0,Enchantment_10_EF43AA5C4B223B705D884DA1FDB9D26D=))
Warning: ImportText (StatID_6_8722CFDC45B1D1F05B1E579647D8BC8A): Missing opening parenthesis: "",Stat_5_32975BDC42BA5A9EF33E269F3491081E=(RemainingHealth_6_B558455141B171C597642CB408C084CE=0,Enchantment_10_EF43AA5C4B223B705D884DA1FDB9D26D=))
Warning: ImportText (StatID_6_8722CFDC45B1D1F05B1E579647D8BC8A): Missing opening parenthesis: "",Stat_5_32975BDC42BA5A9EF33E269F3491081E=(RemainingHealth_6_B558455141B171C597642CB408C084CE=0,Enchantment_10_EF43AA5C4B223B705D884DA1FDB9D26D=))
Warning: ImportText (StatID_6_8722CFDC45B1D1F05B1E579647D8BC8A): Missing opening parenthesis: "",Stat_5_32975BDC42BA5A9EF33E269F3491081E=(RemainingHealth_6_B558455141B171C597642CB408C084CE=0,Enchantment_10_EF43AA5C4B223B705D884DA1FDB9D26D=))
This is the Inventory_item_base:
https://i.imgur.com/uiU4ggE.png
I am using datatable with the struct.
and facing this issue: Unreal Engine Issues and Bug Tracker (UE-40033)