Floorboards finishing a different colour

Hi guys,

I'm having some challenges working out why my floorboards are turning out the way they are. Basically I've hired a floor sander, sanded down my timber floors and then applied Cabot's CPF Flooring (water-based polyurethane).

The challenges I'm having are around differences in colour after applying polyurethane. I've attached a photo which shows an example - you can see the left hand side there's a strip that's noticeably lighter. Now I think I know what caused this, but I can't seem to figure out (googling doesn't yield results) how to correct it. Basically the areas that show up as lighter is the areas that I have passed over with the floor sander twice (once to go from left to right but then I went over a small area from right to left to get closer to the wall on the left). Does anyone know how I can correct this?



The other challenges I've had are that there are some areas where I didn't pass the sander over twice.. but it's still showing a distinctively lighter colour in flooring. Similar issue to above, I'm just not sure what caused it or how to fix it.



Has anyone experienced this? The closest I can see when googling is if someone dropped their drum sander or held it over an area for a long period but I did neither that (the sander moves as soon as its started).

Thanks