Unstable connection

Morning EA,

I really hope you can assist me with the issue I'm having. I have these micro stutters on my line, and I am noticing it mostly when I play FIFA. While I am playing you can see my ping jump by 5ms or sometimes even 30ms every few seconds. I usually play on the Xbox. Here are the steps I took to try and solve it :

- Move ISP ( I was at MWEB before this and decided to move over to you guys )

- Change Router ( I am now using the router that you guys provided )

- I installed FIFA on the PC to see if I get the same issue ( got the same issue )

- Switched everything that uses network off in the house and still got the same.

- I changed network cables ( didn't help )

- I tried playing over Wi-Fi 5Ghz and 2.4Ghz ( got the same issue )

- I setup Quality of service on the router for the Xbox and gave it the highest priority ( didn't work )

- I forwarded recommended ports ( didn't work )

- I switch the Router and the ONT off and left it over night ( didn't work ).

This issue started almost in the middle of the year when FC26 was still out. I am in South Africa. 
My current line is 100Mbps Download and 50Mbps Upload Fibre. This issue is only happening in FIFA and non of my other games I play. 

So far my ISP and Infrastructure Fibre Provider said my line tests 100%

Hope someone can help.