At this point, I'd probably not even bother taking it back and instead I'd just buy a new laptop.
If it's still crashing regularly and their 'repairs' aren't working, it sounds like further repairs aren't going to help either.
Personally, I use a MacBook - I've had one since 2012 and I'm more than happy with it... I'd never go back to a Windows machine now. My MacBook starts up within a few seconds, compared with 10 minutes for my old Sony VAIO to start up, and it runs quickly. Of course, as someone who has programmed a lot in the past, I find Macs more convenient. My only real complaint is with the ports available and the accidental disconnection of the charger/external devices if you knock the cable.
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