Hi! I'm not good with hardware maintenance

Yea yea I know what you're thinking. Why is this thing still in use? Well not all of us are rich ok? I'd rather try to save it than buy a new system, if it can be saved.

So I've had it in the shop for a free diagnosis (I will not owe anything) and they were very transparent that they can definitely see the problem but can't figure out what's causing it. The system will work for about an hour and a half before it massively slows down and eventually becomes useless, even with an external cooling fan venting or blowing inside (tried both). The mouse moves like molasses and programs take ages to do anything. It doesn't shut down but it's basically useless at this point.

They've tried replacing the thermal paste and completely dusting it out (there was lot of dust) as well as some things they didn't say, but they did say they tried a lot of different things to figure it out and it still slows down. They also consulted with someone else who is supposed to be an expert in Alienware, and nothing this person has suggested has worked either. They've basically tried the kitchen sink of ideas, with no results.

The only thing they haven't tried is replacing the whole liquid cooling for lack of parts, so there's no way to figure out if that's what's causing the slow downs.

Would this be what's causing it or is this system just unable to be fixed and it's really time to lay it out to pasture? Is it the video card needing to be replaced?

Thanks in advance if you can help

Could this be the issue?

https://www.dell.com/community/Alienware-General-Read-Only/Aurora-R4-overheating-problem-SOLVED/m-p/5616409#M117996