Question My Gaming Laptop gets fps drops while playing open world games then crashes

Apr 14, 2019
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PC Specs
CPU: Intel® Core™i7 Quad Core Processor i7-6700k (4.0GHz) 8MB Cache
RAM: 16GB HyperX IMPACT 2133MHz SODIMM DDR4 (2 x 8GB)
GPU: NVIDIA® GeForce® GTX 980M - 8.0GB DDR5 Video RAM, DirectX® 12, G-SYNC
SSD: 512GB SANDISK X400 M.2 2280 (up to 540MB/R, 520MB/W)
HDD: 1TB SERIAL ATA II 2.5" HARD DRIVE WITH 8MB CACHE (5,400rpm)

I got my laptop for around 2 years now and it had been working completely fine until around 3 months ago, when playing open world games such as Skyrim or Assassin's Creed Odyssey, the game would run fine for around 30 mins then after that would experience periodic fps drops to around 6-9 fps for around 10 seconds then it would return to normal, then few minutes later, the fps drops again and this repeats until it finally crashes. The odd thing is that this will only happen in open world games and games like Dishonored 2 or DOOM runs fine. Also lowering video settings does not do anything to improve the situation. While playing AC Odyssey I average out at about 65°C on my GPU and around 80°C on my CPU but don't know if that is normal.
I first thought it was a temp issue so I tried thoroughly cleaning out my fans and repasting my CPU and GPU but it did not work. Then I thought it was a driver issue and tried reinstalling my drivers and that didn't work as well.
Not sure what else to try so any suggestions will be greatly appreciated.