lag in dungens and hearthfre houses

[triton1407]

hello,

my problem is, i have strange lags in dungens and the dlc houses
especialy when i look at the ground

my gpu load ist only 25%!
and the cpus cores runs at 20%
settings are all on ultra, aa2x, af16x, 1080p
i run 2 monitors, but i only play with 1
autosave is deactivatet
no mods are installed

outside it runs pretty well, no lags, no frame drops, no freezes at all

system
win7 64bit prof.
cpu: intel xeon 1230v2
gpu: r9 270x 2gb
ram: 2x4gb 1600mhz cl9
ssd: samungs 840evo 465gb