No per se clear error in using decennial census numbers as opposed to more recent ones.
A racial categorization does not lose minority status under the act upon attaining a bare majority in the district; the intensely local inquiry must take into account past discrimination and disenfranchisement.
Narrowness of win does not disqualify the win as proof against bloc voting.
Racially proportional representation is not per se proof that there is no actionable discrimination under the Act.
http://media.ca8.uscourts.gov/opndir/18/07/164511P.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.