More details - hired a company with excellent reviews and a comporable price to two other received estimates. After job completion, noticing significant lines throighout the entire floor. They are mostly visible in direct sunlight, but that room will get plenty of sunlight. contractor came back out to assess and said its because of uneven subflooring. said he will redo but it will happen again due to the uneven subflooring. any suggestions?

They are chatter marks from his equipment not from your subfloor

They don't have the right equipment in their artillery. There is no way they can meet your expectations. with the equipment and process they are using.

It's marginal at best, and unlikely to be the result of loose flooring or subflooring. Before wider employment of multi-disc sanders, this was pretty typical. Any floor refinisher will have a buffer. Used with a hardplate, it can eliminate the chatter you see, though it's quite likely that there's something in their big machine that needs attention. Even if they're using a Trio or something similar, it's a much easier job if your big machine doesn't leave a bunch of chatter to flatten out.

Yes, that area might get a lot of light that highlights flaws, but it will also have furniture and possibly have area rugs and window treatments that serve to minimize flaws. If it bothers you, have it redone, but inquire about how they will alter their process to ensure a better outcome. If it doesn't (or you don't want to take the time for a re-do), perhaps they would agree to do it for half price.

I think it’s so sad that contractors make it “all your fault” when they dang well know (or should know, if they’re any good) it’s their equipment kudos to you for reaching out and getting some expert opinions!

Contractor’s that do this type of quality work, needs to be weeded out. Unfair to compare high quality work to this level. This is why high quality work cost more. we invest in proper machinery and skills to do the job right.