Hello, I am running 5.5.4 and it seems to be more stable with dx12.
I am using nanite and tesslation so I need dx12.
I have found when unreal goes through its phases of not working you are best running in dx11 and waiting it out until a new version fixes their breakages.
Not good… at all.
I am about 6 months behind with development myself (cost me about 12k).