Envy Phoenix Desktop PC stutters / lags randomly

[Orkan4]

Dear Community, 

I have a pretty old HP ENvy Phoenix 850-000nt Desktop machine with the following specs : 

msi kali mobo with rom ssid 2B36,  version A0.08 (Date 08/25/2015)

i7-4790K cpu , 32 GB RAM, Nvidia 970 GTX , 128 gb SSD for OS and boot . 

for almost 3 years now , pc is battling with some random stutters/lags after Windows boots and when logged on to the desktop. After years of searching for a solution I thought it was nvidia graphics driver issue as it never happens on safe mode.  Also I don't recall any lag happened when it was running factory installed windows 8 or the upgraded 8.1 . It ran Win10 pretty well for a long time but along the way somewhere this problem started to occur. 

Long story short I switched to HP provided nvidia drivers for a short period of time and it seemed resolved. But then windows 10 automativally upgraded the nv drivers to latest ones and problem happened againg. I updated the 970 gtx firmware with nvidia provided official one , no good. 

I found a solution with DDU and fixed the display driver to version 472.12 and it's kind of fine. I mean issue sometimes happen but not as much as the latest version nv drivers. 

Last night electricity was cut off for some reason and today I booted up the machine and the random lags on the desktop happened again . So I checked the BIOS and couldn't find anything, also tried to reset the bios to factory defaults several times no good. Tried to flash the bios to an older version which provided officially from the hp support website as follows: 

HP ENVY Phoenix 850-000 Desktop PC series Software and Driver Downloads | HP® Customer Support

https://ftp.hp.com/pub/softpaq/sp71501-72000/sp71809.exe

Interestingly the bios flash utility said my current bios is corrupt but it was upgraded via HP Support Assistant without any errors or issues. So my question is:  could all those lagging problems be related to bios corruption or something like that . 

Bios update error is: 

C:\SWSETUP\[sp71809]>safuwin Ka2_8013.bin /p /b /n /r /reboot
+---------------------------------------------------------------------------+
| AMI Firmware Update Utility v1.02_HP |
| Copyright (C)2012 American Megatrends Inc. All Rights Reserved. |
+---------------------------------------------------------------------------+
Reading flash ............... done
- ME Data Size checking . ok
- FFS checksums ......... bad
- System BIOS image invalid or corrupt.

Thank you and best regards