A cumulative update failed to install on a Windows Insider build, presenting error code 0x800f0990. To resolve this, a Windows repair installation was performed using an ISO file, which allows for an in-place upgrade without erasing personal files or applications. The process involves mounting the ISO, running the setup, and selecting the option to keep personal files and settings. After completing the installation, the problematic update installed successfully, and an issue with the infrared camera for Windows Hello was also resolved.