The first Neuralink implant in a human malfunctioned after several threads recording neural activity retracted from the brain, the Elon Musk-owned startup revealed Wednesday.

The threads retracted in the weeks following the surgery in late January that placed the Neuralink hardware in 29-year-old Noland Arbaugh’s brain, the company said in a blog post.

This reduced the number of effective electrodes and the ability of Arbaugh, a quadriplegic, to control a computer cursor with his brain.

“In response to this change, we modified the recording algorithm to be more sensitive to neural population signals, improved the techniques to translate these signals into cursor movements, and enhanced the user interface,” Neuralink said in the blog post.

The company said the adjustments resulted in a “rapid and sustained improvement” in bits-per-second, a measure of speed and accuracy of cursor control, surpassing Arbaugh’s initial performance.