this happened to one of my 3 card (1080ti) rig, using gminer 1.23, other 3 card rigs works fine..

i put the card in 2 card rig, the card now mines at ~6.9, maybe due to cooler area i placed it in...i noticed that although the gpu core is lower in temps compared to the other 2 1080 ti it simply throttles down from ~6.9 to 3.6 after a few hours...leaving it for now since it is doing ~6.9 in the 2 card rig, will investigate in the future..

i'm suspecting it maybe is throttling down due to heating of the VRMs...happend to one of my 390s back then, don't know if 1080 ti do this too...notice the power is ~240+ watts, that's heavy on the VRMs

edit: it still go down to ~3.7 in the 2 card rig..i think it is a card issue