Glad to hear, thanks for getting back to us!
In case anyone wonders why reassignment is necessary after changing the
Reference name: The
Reference field is the actual property name (used in code and serialization), while
Name seems to be only a the "pretty-print" editor display name. Thus when changing the
Reference name string, the already saved assets see the new name
_MainTex and re-initialize it to null (or a black or white fallback texture) since they don't find anything previously serialized (saved) under this name.