The disruption, which occurred on 28 September 2025 lasted about nine hours, preventing some callers from reaching the Triple Zero emergency network, which is Australia’s primary emergency services number.

According to Optus, 12 users were impacted this time, compared to an earlier outage on 18 September, which is currently under federal investigation and left more than 600 customers affected, resulting in four deaths.

However, Optus blamed Ericsson as the cause of Sunday’s issue.

Meanwhile, the company explained that calls routed through the Dapto tower were not redirected to other networks. While 5G remained active, 4G services failed- blocking calls from connecting.

“We continue to work closely with our technical partner Ericsson, whose equipment did not appear to operate as it should, to understand the root cause of the issue on a single mobile tower in the suburb of Dapto in NSW,” the company said.

“Optus’ ability to detect the outage was impacted as the Ericsson equipment in the cell tower did not alarm that 4G services were not operational.

“At our request, Ericsson has undertaken a full health review of their elements of our network. This review found that what has occurred on this cell site is an anomaly they have not seen elsewhere.”

However, the company reiterated that the tower is fully operational.

Capacity has contacted Ericsson for comment.