Spark Sport says only a "modest number" of customers had streaming problems during Sunday night's All Blacks v Namibia match.
"Spark Sport is happy with how things worked throughout the match with the vast majority of Spark Sport customers having a great viewing experience," a spokesperson said in a statement.
"For the volume of people viewing the match our care teams helped a modest number of customers who for a range of reasons had challenges streaming.
"To help these customers we have deployed some additional care measures to help ensure they have a better Rugby World Cup viewing experience."
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However several from this "modest number" have taken to Spark Sport's Facebook page urging it to "tell the truth" about the streaming issues.
"I am just about to throw something at my brand new LG TV because it keeps glitching out. If you cant deliver the streaming games as promised you should be putting them live on TV!" one person wrote.
"Not even watching it live and it's stop starting, hopeless. Can't even stream our national game at the World Cup properly, it’s a joke," another said.
Multiple users posted photos of their screens showing the streaming errors, including pixelation and buffering problems.
"I didn't pay for this get your act together please," one annoyed user commented, along with an image of their TV.
Spark Sport has been threatened with legal action over its service during the Rugby World Cup.
A group, called The People v Spark Sport, say they will take a class action lawsuit against Spark Sport for $250 million over failings of its streaming service.
When it is filed the lawsuit would claim Spark Sport misled customers about its streaming product.
A number of games have been affected, notoriously including the All Black's first game of the tournament, a victory over South Africa.
However in a statement to Newshub, Spark Sport said it was comfortable they had satisfied their legal obligations.
"As we do with all our customers, we have repeatedly offered assistance to the owner of the Facebook page to resolve her personal streaming issues with Spark Sport.
"She has decided to decline any support from Spark Sport.
"We continue to strongly encourage customers who are unhappy to seek help from us directly and take advantage of our enhanced care measures," the statement said.
Customers with any issues are encouraged to contact Spark Sport via help.sparksport.co.nz.