Maybe try disabling hibernation - admin command prompt:
powercfg -h off

Then go into sysdm.cpl and manually set the swap file size so it remakes it on reboot. I usually do a min of 2GB and max of 8GB.

Then once rebooted, turn hibernation back on -
powercfg -h on

Although hibernation is a piece of trash and always has been and ends up causing weird issues EVERY SINGLE TIME after a while.

UCyborg wrote on Yesterday, 09:53:

... (it's Win10, keeps session in both RAM and disk) ...

FWIW, I still use mostly Win7 but I don't think this has changed much...

When Win7 goes to "sleep" it always writes it's current state to disk.

Often at night or otherwise going away from it for longer, if I see the system is already sleeping, I just cut the power (I have it, monitors, speakers etc. all on a power-bar)

Next time I go to use it and power-on again, it always comes right back to where I left it with never a problem.

I can tell when it's sleeping because the "System has power" LED is flashing - I think this LED is part of ATX spec....
Does your system behave the same way? - Is the LED flashing before you (unsuccessfully) try to wake it up?
If yes: Is it still flashing after you try?
If no: Watch when it goes to sleep ... does the LED start flashing right after?

I doubt there is anything with the OS specifically, same happens on older Win10 install (installed in 2021) as well as newer Win11 (installed late 2023). Yes, nothing special with Win10/11 in that regard, hybrid sleep has been a thing since Vista. Page file is automatically managed.

The issue used to happen once in the blue moon. Now appears more like 2-3 times a week. It seems a bit more likely to happen if I leave the external USB disk plugged in. But I also started using sleep bit more more often, eg. instead of normal (hybrid) shutdown for the night. I reboot every several weeks to clear things up, some kernel memory leaks accumulate over time.

The hardware is housed in a bit of special case (Aerocool V-Touch Pro), no traditional LEDs, a touchscreen that only has separate HDD activity indicator in place of LED, which is non-functional...or rather perhaps only works for IDE disks while I use SATA. I'd have to check to be sure, but I'm almost positive the HDD LED wire is plugged in the right place. Screen is just dimmer when sleeping / hibernating / fully shutdown. It's normally bright when in this frozen state.

Windows has been reporting corrected hardware error on AMD Northbridge for many years now though, always when resuming from either sleep / hibernation (which includes Win10's hybrid shutdown, which basically logs off users and hibernates kernel).

1A corrected hardware error has occurred.
2
3Component: AMD Northbridge
4Error Source: Unknown Error Source
5Error Type: 14
6Processor APIC ID: 0
7
8The details view of this entry contains further information.

Details tab has this to say about the event:

1ErrorSource 0 
2ApicId 0 
3MCABank 4 
4MciStat 0x80000010000e0c0f 
5MciAddr 0x0 
6MciMisc 0x0 
7ErrorType 14 
8Length 936 
9RawData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

I spotted this error randomly at some point in time, no idea when it started happening and if it's related. Well, it's not young anymore and no computer before it has been as reliable. Wouldn't be surprised if the extra slower stick of RAM, the Kingston, which was only installed 2 years ago, is a bit flakier. Guess I could run some stability test to see if things are still stable, I haven't noticed anything odd otherwise.

I've read somewhere power up is supposed to be most stressful for computer. Not sure if resuming is supposed to be equal, no issue with normal power up, just when session is kept in RAM.

UCyborg wrote on Today, 13:54:

... no traditional LEDs, a touchscreen that only has separate HDD activity indicator in place of LED, which is non-functional...or rather perhaps only works for IDE disks while I use SATA. I'd have to check to be sure, but I'm almost positive the HDD LED wire is plugged in the right place. Screen is just dimmer when sleeping / hibernating / fully shutdown. It's normally bright when in this frozen state.

Do you have another case or means of connecting the normal power-ON LED?

It would be very helpful to know what state the system thinks its in .. does it actually know it's sleeping?

The display "could" monitor the power-ON LED line and dim when it flashes, but I think more likely it's related to power supplies, as some things get shut off while sleeping.
But you can't tell if going to sleep completed correctly when going to sleep, and/or if it still knows it sleeping by the time you try to wake it up.

If you can find some way to monitor the LED output that might help....

Could this possibly have to do with the +5v sb rail being iffy? I seem to remember similar issues in systems once upon a time when the capacitor plague was a big thing. Since the +5v sb rail in PSUs is usually pretty low spec and low tech, it would usually be the first to get out of whack once it's filter cap started going bad.

I don't have any other case. But the bad +5V SB rail theory sounds logical. Leaving external HDD plugged in must add to the load, I remember hearing the disk in this case while computer was silent. So in theory, the easiest fix would be replacing the power supply and see how it behaves?