Random sleep mode issues

[Nahtan]

Hello
I recently bought a used Lenovo T420, it has some weird issue with sleep mode.
this presents itself in some different ways.
it goes to sleep but shuts off completely after one second(standby light goes out)
it goes to sleep normally(standby light stays on) but it will boot as if it was in hiberation mode (this option is not available in the menu) and resume operation
it goes to sleep mode but shuts off after an unspecified amount of time, it may take 2 hours or much longer

the laptop is always in on the desktop dock as I use it for light duty work such as browsing and watching videos, so it is always supplied with power.
the battery is fairly new, I recon the previous owner just replaced it, but it's a knockoff.

these symptopms may change with a different windows power plan(even with all settings being the same) or they may stay unchanged
I have tried all manner of settings, I even installed a custom bios (Oleh's mod bios based on v1.46) with advanced settings available and played with the power management settings a bit, enable/disable C states, PCI and CPU power settings and what not

interestingly, the "Powered USB" settings seems to change the behavior for a while, no matter if you turn it on or off, just changing the setting seems to make the symptoms better for a while, until they come back.

I'm at my wits end by now.

take today as an example.
the laptop crashed overnight after just 4-5 hours, I sent it back to sleep when I left for work, then it booted from standby when I came back home after 8 hours.

If anyone got any idea what's going on here, I'd really would appreciate your input, even if it turns out there's witchcraft at play here, I just wanna know what's going on.

[Nahtan]

push?

[Nahtan]

it's real quiet here...

[Nahtan]

can nobody help me here?

I reinstalled windows, it worked for 3 days, now it's back to how it was

[Nahtan]

I changed USB settings to "charge with always on USB port" as "enabled"
standby works again, until it doesn't...
uninstalling the latest windows update did nothing tho

[Nahtan]

so....no help from the forum?

I also get some other random issues, like dramatic performance drop even tho CPU usage appears normal
CPU randomly gets locked to 30% usage at less than 1GHz, won't go above or below 30%
sometimes sending it to sleep and waking it up again helps, other times I have to reboot, and occasionally take out the battery and unplug the laptop for a few minutes.