Windows 11 is facing significant issues following the January Patch Tuesday, particularly with boot failures on commercial devices. These problems are linked to both the January update and a flawed December update, leading to a "UNMOUNTABLEBOOTVOLUME" Blue Screen of Death (BSOD) error. Microsoft has indicated that devices that did not successfully install the December security update are left in an improper state, which can prevent booting when subsequent updates are attempted. While Microsoft is working on a partial solution to prevent further installations that could cause boot failures, this fix will not resolve issues for devices already affected. The company is investigating the causes of these update failures and their consequences.