The Pyrosphere door glitch, also known as the Sector 3 door glitch, is a potentially disastrous bug in Metroid: Other M involving a locked door found in the basement of the Desert Refinery, which completely halts progress, leaving the player unable to continue without starting over or using an old game save taken before the bug occurred. Consequently, copying the save files to the other does not solve the issue. Nintendo later acknowledged the glitch and revealed its cause. If the player encounters this glitch but do not wish to start over, a fixed, non-glitched save file of this door for the US version is available for download.