Trouble shooting a 1080ti card that is slowing down

Hey all, I got a small mining setup (since mid Jan.) with 2 GPUs running DSTM. The MSI card (90% pwr) runs fine with no problem. Recently I begin to notice that the EVGA card is getting less and less stable unless I dial down the OC setting. Initially, I was running stable (24 hours+ up time) +120 core and +300 mem at 90% power and getting ~750 Sols/s but in the past week DSTM starts to crash and I would have to gradually reduce the OC setting for the EVGA card for it to run stable. I go back and forth on it in the past week battling with this card and now I can only reach stable mining at 90% with no OC at all (670 Sol/s). DSTM would crash immediately if I try to use the stock card setting.

Currently, the stable clock is ~1740 / 5000 mem (no OC at 90%)

Things I tried: -DDU and install fresh driver. -Fresh windows install. -Swap risers (bought a 6-pack) and switch between the PCIEX slots. -Using only the EVGA card (on riser or directly on MOBO). -Tried nicehash, EWBF, and bminer. None of these helped.

Any suggestions on what could be the problem? Any help appreciated! Thanks in advance!

OS: Windows 10 GPU: 1x EVGA 1080ti SC black. 1x MSI 1080ti gaming
PSU: EVGA 750 G3

Open air, using mobo graphic for display. Using MSI Afterburner. Both card temperature kept at mid 50s. Powering the risers using 6-pin directly connected to PSU.

When I tested DSTM, first thing I noticed was that it is really picky if you overclock your card above what it DSTM already has set. I could make small changes until I thought it was stable , but a few hours later, it had rebooted and reverted back to stock settings.

Have you updated to version 6 of DSTM?
You may want to try EWBF and see if the problem persists or just with DSTM.