Neuralink’s brain-computer interface device has encountered issues since it was implanted in its first human subject, according to the company owned by Elon Musk.

Some of the device’s electrode-studded threads started retracting from the brain tissue of quadriplegic Noland Arbaugh about a month after it was surgically implanted in late January, causing it to transmit less data, Neuralink wrote in a blog post on Wednesday. 

The Wall Street Journal first reported on the malfunction that caused a reduction in bits-per-second, a measure of the speed and accuracy of the patient’s ability to control a computer cursor by thinking. 

Neuralink made up for the malfunction with multiple software fixes, resulting in a “rapid and sustained improvement in BPS, that has now superseded Noland’s initial performance,” the company said.

The company is now focused on improving text entry for the device and cursor control, which it hopes in the future to broaden its use to include robotic arms and wheelchairs. 

Neuralink in September said it had received approval from U.S. regulators to recruit human beings for the trial as part of an effort to use technology to help people with traumatic injuries operate computers with only their thoughts.

The Food and Drug Administration approved the trials of the device, which has not been given broad regulatory approval needed for widespread or commercial use of the technology.