HP Z240 SFF (i7 6700) - post screen sometimes shows it shut off on overheating (not true at all)

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I have an old HP Z240 SFF with intel 6700. Yes, it is is a hot box and a POS. But the CPU can stay at 70°C if I leave the case open. It also NEVER shuts down or throttles due to heat.

 

The most demanding task is watching YT. Other tasks are just browsing or remote work. So the CPU really isn't taxed at all outside YT 4K videos. I use dGPU and often I have to set YT to 1080.  

 

But sometimes when I start it up (cold) the BIOs gives me a post sign it shut down on overheating. This is totally not true since before shutting down i unusually just browse around and don't' stress the CPU. I also watch temps with HWinfo64. When that Post comes up, I just turn the PC off and on again and it works. This only happens every 10th start. But i think it happens more often. 

 

I tired to update BIOS. But have no idea if this is the correct BIOS since those Z240 also seem to exist with Xeons. Executing that files give me this error. 

 

 

I have W10 fresh install. so i don't have whatever HP OS came with it. Has 16GB RAM and SSD.

 

1. Is there a way to get the correct recent BIOS?
2. Should I worry at all as long as actual temps are fine? 
3. Are those signs of a failing PC? 

 

I know PSU/MB are proprietary. If this PC croaks, i have a MB of the same generation that could use the quadcore and the RAM (that PC only has a dual core and 8GB). So this PC dying isn't the end of the World. It came from a business that had them running 24/7.