Streaks and lines

Hi
I wonder if anyone else has this issue or solution to it  suddenly we noticed some lines on our floor tiles where we use our L40s pro ultra for mopping. This was not happening before. I can not rub them out either with hand mopping over them  
I have checked, all wheels are freely rotating and nothing else is dragging along so not sure what has caused these lines
Any help will be appreciated
Thanks

Have you watched it to see the lines appear as it does it. Should give you an idea to what causes it.

Hello,

do you mean the black streaks or lines? If so, we recommend checking whether the main brush shows any signs of wear. If it is worn, please replace it in time.

In addition, you can remove the main brush cover, clean it thoroughly, and then reinstall it properly.

Hello,

Thank you for your reply.

Could you please upload some photos to help us better determine the possible cause of the marks?

Here are two images and 2 more in next one

Hope you can see the lines  they are more prominent in day light  

Ok. So looking at the photos. I’m going to make a suggestion.  Buy a good tile cleaner. Something that does a deep clean.  And clean one tile.  It looks like the lines are due to the tile being cleaned back to what it should be.  Over time tiles get dirty even with mopping.

But get a proper cleaner on them and see what happens.

Greeting，

You can also check whether there are any worn areas or scratch marks on the main brush cover. We have previously received feedback from customers reporting that the main brush cover was scraping against the floor.

We hope this helps.