It seems it is a known problem of the cotangent frame computation: see the comment from Zagolski in the comment section of Followup: Normal Mapping Without Precomputed Tangents | The Tenth Planet (we are using the computations described in this article to compute the tangent/bitangent).
Indeed, your uvs are very closed to each others in the areas that exhibit the problems and there’s not enough precision to compute a sensible tangent vector. As a workaround, you could try to provide your own tangents with the model geometry, in addition to the position/uv.
Here’s a closup with the tangents displayed on the right:
https://www.babylonjs-playground.com/#FS3SF2#4
We can see in this PG that enabling Realtime filtering does not fix the problem, it only changes a bit the colors on the left, but the right part remains the same.