4.12’s fix of ConvertTransformToRelative did not change the parameter names, meaning the function appears to provide the inverse i.e B->A not A->B after being fixed in the release log.
This example blueprint worked before the fix but now gives an inverse location. The socket’s world position (53,53,53) is converted to relative with the parent actor’s transform. We would expect this to be 53,53,53 but this is now being returned as -53,-53,-53 as the transform is actually from the ‘Parent Transform’ parameter to the ‘Transform’ parameter.
Although this is covered in the function’s comment, it is not obvious from the blueprint node or the function parameters.