Question Unsure what's wrong, is it my network or my PC

[Able6actual]

Hello
I hope someone here can help me. After watching endless hours of PC's being built on YT, I built my own PC. I was surprised, but it worked flawlessly on the first boot and has been running great for about 8 months. Here is the issue. Recently, I have been experiencing horrible lag when I PC Game. I mainly play games on Steam and on the EA App. I have upgraded my Internet speed to the best package offered by my ISP (Cable with 500Mbps Download and 22Mbps upload and my ping is usually 10ms) And have swapped my old modem for a brand new one and switched from wirelessly connecting through my ASUS RT-AX82U router to a wired connection (Through the gaming Ethernet port on the router).
I have had service techs come to my home from my ISP and check all the cable lines from the modem to the telephone pole, and they insist nothing is wrong.
Running speed test, I have seen a slower download rates by about 150 to 200Mbps, but only usually in the evenings when I think a lot of people that live near me are on the net.
Here is the weird part I can't understand. I have all along thinking it's ISP or Service related until three days ago. I joined a Battlefield 2042 room and the lag was unreal. I left the game and shut my PC down. I waited a minute and booted the PC back up and rejoined another Battlefield 2042 game and everything was normal. I did not reboot the cable modem or router, just the PC, and the lag was completely gone. Yesterday I connected to a game on steam and had crazy lag. I shut the PC down and rebooted it and things were fine again.
I used Google to see if there could be an issue with the PC, and the only suggestion I could find was to check and see if I was missing any hardware or software updates. I checked for CPU, Motherboard and GPU and OS updates and everything shows to be current.
I am stuck and hope someone here can help me.
MY PC specs ....

Motherboard - Gigabyte Z590 Aorus Ultra
CPU Intel 11thgen i9-11900
Memory - Patriot Viper Steel DDR4 64GB (2x32gb) 3200Mhz
GPU - NVIDIA GeForce RTX3070Ti
OS Windows 10 Pro
Storage Samsung SSD 970 EVO Plus 2TB
Case - Corsair Carbide Series 200R Compact ATX
CPU Cooler Mugen5 Black Edition

Able6actual

 

[Wuwu]

System temperatures? What CPU cooler? What PC case?

 

[Able6actual]

The Case is a Corsair Carbide Series 200R Compact ATX Case
CPU Cooler is a Mugen5 Black Edition cooler
Using HW Monitor, Under Mother Board - CPU is 59 Degrees C. Under Intel Core i9 the package high temp was 67 degrees C and the Max Cores 65 degrees C. The GPU shows max 49 degrees C, Memory 56 degrees C and Hotspot 59.8 degrees C

 

[Wuwu]

Run Cinebench (Latest) on the CPU, report back temps.

Run Unigine Superposition (1080P Extreme) on the GPU, report back temps.

 

[Able6actual]

Running Cinebench 2024 - cpu temps max 63 degrees C on MB - CPU temp was 51 degrees C
Running Unigine Superposition (V1.1) at 1080P Extreme Min temp was 46 degrees C and Max was 81 degrees C

After both tests, I had a BSOD with regard to memory management. The PC rebooted and seems to be running fine. I never had a BSOD before on this pc though

 

[Wuwu]

Memory is unstable.

 

[Able6actual]

So you suggest I replace the memory?

 

[Able6actual]

After running memtest86, I located and replaced a stick of bad ram, which fixed some of the issue. After complaining to my ISP, they sent a tech out and found the cable line from the service to the house was in bad shape, and they replaced it. So far things seem normal, but I will watch it.