GPU Core/Memory clock started acting funky for no reason

[R9380RULES]

I have a Gigabyte GTX 1060 6GB WINDFORCE OC which I got 5 years ago, it used to work fine but now the frequencies increase randomly even if I'm doing nothing, also launching MSI Kombustor (the menu, not a stress test) triggers the frequency increase. I'm worried about power consumption and have set the Power Plan to "balanced" (Windows) and Power Management Mode to "optimal power" (Nvidia), I remember that setting it to "prefer maximum performance" made the GPU always run at full speed but now the speeds don't change as if another program is overriding my settings. Moreover the boost frequency it would reach under load has been decreased by ~100MHz and it fluctuates back and fourth constantly, I know that performance can be reduced to maintain a safe temp but my GPU's temps are the same as before (70C under load) and the frequency used to be more stable. I haven't installed any shady apps or changed some setting I didn't know about, how could I fix this? Would reinstalling the Nvidia drivers help? I've already deleted the Nvidia files in ProgramData, reset my settings in the Nvidia control panel (Use the advanced 3D image settings is selected) and took apart the GPU to clean it and re-apply thermal paste but it's still the same.
Note: The GPU usage is still close to 100% despite the frequency reduction and according to MSI Afterburner the usage jumps for a moment which is what's causing the frequency change, but I don't know why it's not staying at 1% while idling.