Following the Unreal landscape tutorial :
I have created a Landscape from a heightmap of 249x249 : 8x8 components of 1x1 section of size 31x31 quads.
I have assigned a landscape material with 4 layers.
I have created, for each layer, a Layer info for painting.
I have exported, for a layer roads for example, a weightmap (in raw format).
When I import this weightmap (in raw format) for an another layer (or the same) I obtain this message :
“The layer file does not match the current Landscape extent (249×249), and its exact resolution could not be determined”
Moreover, the size of the weightmap is exactly 249x249 bytes !
I have done the same thing on 4.12 version without error.