The CRR0027 Code Analysis (Possible Null Reference) misfires in cases where it is syntactically impossible for the variable in question to be null - specifically when the variable itself is a Value Type.
This is easily reproducable by enabling analysis and applying against a document containing the following repro class:
public class FalsePositive
private bool _x;
public string X => _x.ToString(); //This line generates a CRR0027
Doing a check on the nature of the variable(Ref Type or Value Type) would provide an immediate escape from further anaylsis.