Had similar experience with the software activated again after using the majorgeeks tool. So this was useless.
What I found to work so far was keeping the software installed, and turning the Perioritization Engine off, and also disabling Auto Bandwidth. This will prompt for setting a bandwidth. Set the up and down speeds to something like 1500 MB.
This I found on the Dell website at this link: https: //www.dell.com/support/kbdoc/en-us/000135709/slow-internet-speed-using-killer-ethernet-adapters
I do have XPS 8930 and this did the trick for me . I hope this works for other models or brands.
So far this solution has worked. I have turned the PC on and off for several weeks and the UP and DN speeds are normal at the ISP nominal rates, and those settings at the Killer software have stayed the same.
Cheers.....