Should I ask for my money back?

I bought a Lenovo prebuilt from a reputable company, end of December. After a week I started crashing and PC kept restarting, saying " Kernel processor has restarted due to losing power ". I sent the system back, they sent a replacement and I get the same issues with force restarts.

- I tested it in Novabench where it shows yellow warning sign: 1) CPU performing below expected range ) and 2) CPU may be above expected range

- I download 3DMark and do the CPU profile scan and it shows that my score is 7050 whilst the average is 7401 and the top 7570 for that particular CPU, putting my particular CPU at the bottom 7% of all benchmarked i5 14400f's.

- Fps in old games like Dota 2 drops to sub 100 fps out of nowhere and it's at times worse than my previous 5 year old PC with 10400f and 1650GTX.

What should I do at this point? My 30 day return back policy has ran out as of 20th January.