The repair deadline has now been put off indefinitely with the errors being discovered in two different branches, an Internet service provider said Sunday.
In December and January this year the cable had an issue with the connection to Hong Kong, Japan and Singapore. They affected the entire line.
A problem with the connection to Singapore and Japan was fixed in March, while work to repair the Hong Kong line was delayed until the end of April.
In June repairs to that branch were completed, restoring a vital Internet connection between Vietnam and Hong Kong.
But by then, the S1.7 section on the cable, which connects with Singapore, was malfunctioning, resulting in data flow declining to half its normal capacity.
Even as S1.7 was being repaired, two more errors were found.
Now, Vietnam has completely lost Internet connection with Singapore on the APG cable.
But the impact on users is not expected to be significant.
During past cable breaks, especially when all five broke at the beginning of this year, service providers in Vietnam always found solutions, such as distributing network traffic equally across a pool of resources and purchasing bandwidth to improve Internet capacity.
Vietnam has five undersea cables in operation and the other four are operating normally.
Four local companies, FPT, VNPT, Viettel, and CMC, own the 10,400-km APG cable along with a group of international businesses.
With a maximum bandwidth of 54 Tb per second, it has the highest capacity of any undersea cable in Asia.