Floor refinishing looks bad - rootcause?

[Sylvia Schumacher]

Hi biggerpockets forum!

I got a hardwood refinishing job for a SFH. My contractor sent me the picture attached below today (1st layer of stain).

All floors are sanded already, only this one room is stained with the first coat. Can anyone share advice on what has gone wrong with these floors? Is it possible to tell from the pictures if it's related to how the stain was applied or whether it's related to a bad sanding job?

What are my best options? For that room below, would a second coat of stain be helpful to even things out a bit? Could I just apply sealer in the other rooms to avoid that the unevenness is coming to the surface?

Thanks!

PS: Not looking for a GC or PM to reach out to me letting me know I can't do it and that I need their help for everything. I understand that I am learning and I may make (expensive) mistakes but I also consider that as part of the learning journey :)