Thanks a lot for sharing DruBan
The solution turned out to be removing the texture I was not using for the given UV map.
Initially I was using the same grey-scale file thinking that it was enough by unwrapping only the area I needed for that UV map and placing it only over the texture part of the file that I needed. But unfortunately for some reason the rest of the model was being unwrapped too. The rest of UVs were being kept under the ones I had purposely unwrapped. And even though at some point once I noticed this, I was scaling the unneeded UVs down to a tiny size and even moving them out of the UV area, they were still being used
Btw, I had create a new file per UV map too.
Anyway, glad this is no longer a problem.
Btw, I gave a try to the Vector/Bump node, but didn’t notice much of a difference. Good to know though.