If most of the floor looks fine, chances are it's defects in the flooring.

We put in 3/4" hardwood this spring and it was amazing how many defective boards we had to pull out of our stack of floor boards. Some were crooked as a dog's hind leg, some thicker, thinner, narrower or wider than the rest. I have one spot where we didn't see that the board was narrower so I have a larger [we're talking maybe a 1/16 of an inch] gap between the boards. And we bought quality flooring from a high end flooring store......

The nature of Koa flooring is that it will have a lot of variation, some of the characteristics you are showing in the flooring appear to be a result of that natural color variation. However, milling defects are within the control of the manufacturer based how the wood is dried, the milling process, if they measure tolerances (thicknesses) during milling, and other quality control measures. But if you purchased it from a retail store, they may not have first hand knowledge of the manufacturing processes and quality control, and hopefully you have a cutting allowance factored into the order. A reputable supplier should be able to address your concerns. If you are working with a professional installer, make sure they assess the flooring prior to installation to determine what additional steps, if any, will be required to "make the material" work, you may want to allow extra time for installation and sanding afterwards. Good luck!

If this is an unfinished floor, some of this can be addressed during sanding (some...not all). If this is "factory finished" then we have a problem.

No matter what, stop the install and start checking the thickness/widths of all the planks. Start putting them into different piles according to physical thickness/width. The planks that are completely unusable = waste (that includes 5% already stated above. Document everything you have to done to cull/sort the different planks. Try to figure out square footage for each "category". You will then forward on your documentation to the "point of sales" and see if they can offer discounts or replacements.

If you can gather together enough of thickness "A" to finish a room, you should try to do so. It is up to the installer to do some of this work. It is up to you to deal with the point of sales to get a discount on the materials if you find there is more than 5% product that had to be culled or falls outside of manufacturer's milling specifications you can get that discount.

Thanks everyone for the suggestions. We ended up asking the installer to remove what's been installed, sort the planks and try getting enough good ones to finish a room while I reach out and deal with the supplier.

Is it a factory finish? Just curious.

Yes this is prefinished.

Ouch. The supplier is going to have a hard time with this (not your fault...but still). Probably no way to sand and refinish to get these flat and even.

Where did you purchase the flooring?

Having the result be that uneven could be BOTH your product and installer -- and/or your subfloor may also need leveling in places so check that, too. If you've not already put down too much to return the product and start over and if the sorted boards appear to be more than the "standard 5% waste", you might consider going with a different product.

No, you're NOT being too picky -- those uneven boards represent a safety/stumble risk. Now is the time to deal with it.

Again, who did you buy the flooring from?

Sophie, I am in contact with the supplier to resolve the issue right now so don't want disclose its name before they at least have a chance to respond. Sorry.