Hi,
I found a wrong validator rule for background-position-y property.
In SonarQube the rule is
background-position-y < length > | < percentage > | left | center | right
but should be:
background-position-y: < length > | < percentage > | top | center | bottom
(https://msdn.microsoft.com/en-us/library/ms530720(v=vs.85).aspx)