Hey wielkiczarnyafgan -
There are a few things to check. First thought, your model itself does it have the actual gaps in the planks or is this merely created with texture and normal map on the flat model? If the gaps are actually in the model you may want to look at widening the gaps just a touch as the Temporal AA may be causing the jagged edges. You can test this by switching the FXAA in your Post Process Settings and see if the jagged edges go away.
If on the other hand, you have created entirely with textures, then it is probably a mip generated setting which is causing your to have the jagged lines. You may want to try to use a Blur setting on the Diffuse and Normal to see if you eliminate the edges.
Let me know -
Eric Kethcum