Bought a used laptop and now tested it: Significance of errors in the OCCT test?

Last week I bought almost the same laptop as a used device online. The reason: I want to upgrade my device in terms of processor and RAM [and now with the "new" device there's still the option to switch to an NVMe SSD -> another question from me].

My previous device has an i5-6500T (with HD Graphics 530 graphics chip) and 8GB of RAM as well as a Crucial CT525MX300 SSD.

The new device contains an i7-7700T (with HD 630), 16GB RAM and (in addition to a 2TB HDD) a Western Digital NVMe PCI-SSD [I don't know which exactly].

My problem: After an extensive virus (etc.) test, I have now also tested the PC with various benchmark and test tools. Including the CinebenchR32, Prime95 (2 hours) and above all the tool OCCT, which I have never heard of before.

At OCCT, errors occurred more or less immediately in all tests (Linpack 2019; CPU test with "data set large"; RAM test). In the Linpack test, one every few seconds. With the RAM test the same, with the CPU test then at some point always 5-8 errors per refresh. That was the case with the first tests.
But maybe a little specialty here: I carried out the tests while the device was plugged into its docking station. It is one of the kind we know from the corporate sector. The laptop is plugged in and, as far as I know, connected via a PCI interface. The docking station supplies electricity via the power supply unit, which is also used to operate / charge the laptop. [It's the same with my previous laptop, which also has the same docking station].

Today I ran the tests and no longer operated the computer on the docking - instead connected it directly to the power supply and let it run without a battery.

In the subsequent tests, no errors or only one test error were output. And none in the Linpack 2019 and in the OCCT CPU test. During the RAM test, there were no errors for a quarter of an hour, but then until the end of the 30 minute. Test running again error.

What I'm getting at: I used to be more into the matter. Gambling, handicrafts and screwing, OC, testing, benching. But I'm now 10, 15 years older and, above all, I'm not yet familiar with the OCCT tool. So far I haven't been able to find much in terms of expressiveness. Lt. Self-description of the tests, they all provide a very good source of error detection.
But I would be happy if someone could answer me: What significance does OCCT have?

I still have Prime95 running today. In my opinion, the system remained stable for over two hours [I know, it's not that long, but it's not an oc system]. No crash. I also plan to use Memtest86+.

In principle, the computer is running. Windows 10 was installed by the seller - but on a computer that, to my knowledge, comes with Linux from the factory.

Unfortunately, I have not yet had the opportunity to use the computer and test it for longer (i.e. To use it normally; apart from the above-mentioned stress test, which ran for a few hours in Windows without crashes, image errors or the like; I also forgot the FurMark which ran for half an hour).

To be honest, I have to say that the trackpad / mouse control panel or even the mouse pointer spun around quite a bit [delayed reaction, jumping to another place; a bit like externally controlled] AND to my great horror the computer once showed strong image errors shortly after starting Windows. The whole picture flickered, mostly black, with some artifacts on the screen. In between the desktop reappeared, then again errors.

So I'm not sure if the hardware is kosher or damaged. The device was reportedly only used for 7 months. It looks - especially compared to mine - quite new, little used. The seller really exaggerated with the indication of signs of use. Furthermore, I get 2600 hours of operation for the HDD, i.e. + - 3 months.

What do you all mean?

Do that with the Memtest via USB Bios, I'm curious whether at least the RAM is OK.

Maybe it's just the HDD, the laptop doesn't have an SSD? This has happened to me before, the laptop fell from a quarter of a meter when it was switched on, and the hard drive was constantly frozen and sounded different, maybe change it, preferably with an SSD.

Yes, I will do that. Also test mine with OCCT and see if it also produces errors [that will cost me nerves, if so]. So far it has been with me for 6 years under Win 8.1 and actually runs well. Only recently two failures of the image that only came back when the CMOS battery was taken out.

No, it can't be. The OS is installed on the NVMe, if I'm not entirely mistaken. And through an HDD error, the various tests would not output any errors, I would now say. They have nothing to do with the HDD.