I haven't tried switching back to DX12 then down to DX11 again. It'll be about 11 hours before I'm home from work, unfortunately.
I'm not sure if it is universal to those experiencing stutters, but any input (changing direction, opening menu, etc) is non-responsive during the stutter.
Since input issues coincided, i toggled 'reduce input latency' to off, with no change noticed. This was in DX11 after having switched back from DX12.
Also, according to my system monitor, I wasn't pegged on RAM usage, so i don't suspect a memory leak. About 90%/100% CPU/GPU usage typically. Haven't seen any CPU spikes, but i didn't have a trend of that data either.