The engineering team at the space agency is currently investigating the situation on the probe, which is currently flying through the intersellar medium.
The data received back on earth has led to some head-scratching - but what does it actually mean?
Here’s everything you need to know.
What data has Voyager 1 sent to Earth?
NASA released a statement on 18 May which said a team was currently investigating “the source of a system data issue”.
According to the agency, the Voyager 1 probe is “operating normally, receiving and executing commands from Earth, along with gathering and returning science data.”
However, it is believed the information and data it is sending from the explorer “don’t reflect what’s actually happening onboard”.
NASA says an antenna attached to Voyager, which is pointed at Earth to send data back, appears to be working but is sending back the invalid data.
Are NASA scientists worried about Voyager 1?
Despite being left confused by the data, the engineering team at NASA aren’t too concerned about the condition of Voyager 1.
In a statement, the agency said: “The issue hasn’t triggered any onboard fault protection systems, which are designed to put the spacecraft into “safe mode” – a state where only essential operations are carried out, giving engineers time to diagnose an issue.
“Voyager 1’s signal hasn’t weakened, either, which suggests the high-gain antenna remains in its prescribed orientation with Earth.”
Suzanne Dodd, project manager for Voyager 1 and 2 at NASA’s Jet Propulsion Laboratory in Southern California, added: “A mystery like this is sort of par for the course at this stage of the Voyager mission.”
How long has Voyager 1 been in space?
The space probe was launched into the Solar System in 1977.
It has been operating for a total of 44 years, with its mission extended to explore the boundaries of the outer helisphere and the interstellar medium.
The extended mission is expected to last until 2025, when certain elements of the spacecraft will no longer be able to power the scentific instruments onboard.
Ms Dodd said: “The spacecraft are both almost 45 years old, which is far beyond what the mission planners anticipated.”
Previously, Voyager 1 had made notable flybys of Juptier and Saturn, as well as Saturn’s largest moon Titan.
Where is Voyager 1 now?
Ms Dodd confirmed the space probe is currently in the interstellar medium, saying: “We’re [also] in interstellar space – a high-radiation environment that no spacecraft have flown in before. So there are some big challenges for the engineering team. But I think if there’s a way to solve this issue with the AACS, our team will find it.”
This makes Voyager 1 the first ever spacecraft to have passed through the heliopause into interstellar space.
It first reached it in August 2012, and has since sent back data which confirms its location.