FPS drop from Solid 60FPS to under 5 FPS after 10 minutes on Macbook Pro 2017

Earlier this month I was playing with great FPS for what a Mac is and its renowned reputation for poor gameplay. However, upon returning to this patch, I have found that after the 10 minute mark (give or take a couple minutes) I start to drop in FPS. This drop increases as the game progresses, ultimately the game is that frozen with players teleporting etc.. that it is utterly unplayable, abilities, basic attacks and farming is absolutely impossible. It took me 20 seconds to hit the 'X' on the top right of the shop when I based because the cursor was that frozen i had to estimate how much I needed to move it to land on the exit shop button.

Here are my attempted fixes which have not been helpful to me so far:

• Updating Macbook (my updates are automatic anyway) *Changing the display to Non-retina when in game (Worked for me back when I had a similar problem in early 2017) *disabling the shake cursor to show location setting
• adjusting in-game video settings (Whether I play on 'very high' or the lowest settings, it does not impact this huge fps drop as the game goes on, Vsynce changes are insignificant to this also)
• disabling in game sound (little to no improvement on this issue)
• plugging the macbook in rather than using the battery (this is a no-brainer)

In before the ''Gaming on a mac no wonder'' comments; I have a functional gaming computer however I can't exactly transport it efficiently during my vacations from studying away from home.

I hope to have some insight into this issue as it is quite recent and I find it rather unusual how I can run the game in the early stages with ease and then it is worse than I imagine trying to play Max settings Player Unknown's Battlegrounds on a 1977 Atari console.