I'm not familiar with this manufacturer, but if this was a pre-finished product, I understand this is typical. The height differences between plans should be minimal and there shouldn't be cupping or buckling, but height variations nonetheless will exist.

Thanks Marc. By pre-finished product do you mean that there's more work to be done on the floors once they're installed? If so, what kind of finishing? Would it help smooth out the surface to further minimize the height variations?

Pre-finished as the stain (optional) and top coat (usually polyurethane or similar) was applied in the factory. The job is done once the wood is stapled/glued down.

Site-finish is when the wood is stained and finished in the home after installation, When you do this, before applying stain/poly the floor is sanded smooth.

So in a site-finish job I would expect smooth floors. But with pre-finished, they don't get sanded down on-site so there can be slight variations between planks.

@Marc12345 any suggestions on we fix the slight variations that are there between planks, I just got done with the installation of pre-finished hardwood and it is not a good experience walking on the floor because of just millimeter of height differences that are there everywhere at the joints. We feel it specially when we walk across the planks.