Recently, some users reported the error message “sihost.exe – System Warning Unknown Hard Error” (also known as sihost.exe unknown hard error) when accessing Windows 10, especially after getting Windows 10 April 2018 Update 1803. This error has also occurred when launching a program or game or even after going through a Windows rollback cycle.
Other error messages sometimes appear, such as Ctfmon.exe unknown hard error and Explorer.exe unknown hard error. These error messages may indicate damaged or corrupted system files in your operating system or conflicts between third-party software and your upgraded Windows system. To solve this problem, you can try the solutions listed below.