I have a Dell Inspiron and I just recently switched the palm rest and base cover. These are two very trivial fixes and to be honest I wouldn't expect them to have any direct cause in this issue. Since replacing them my computer refuses to perform a hybrid shutdown using fast startup. It will instead close all the running applications, shut the screen off while the keyboard backlight, CPU fan, etc. continue to run, only to return to the lock screen. Since then I've contacted Microsoft several times on the software side of things and I've taken a look at the hardware myself.
Everything looks and runs fine aside from this shutdown. I know some workarounds are to disable hibernation or to turn off fast startup but honestly it's not something I'm willing to compromise on. I want to have fast startup and simply running away from the issue isn't an option for me. It's worked fine up until now so I'm not sure what's going on all of a sudden.