Since I use my S5 Max to mop every day (because our pup just can't stay out of puddles) I noticed two problems:

1. The mop cloth is too flat so if there is any little curve in the surface, like on tiles, it won't mop properly.
    
2. I have the water flow set to max and when the cloth is pressed against the surface, it is not absorbing the water fast enough making it spill over the top of the mop cloth plate. 

This is why I made this insert, which is slightly slanted, making sure the mop cloth has a perfect contact with the surface and I have also added water flow channels, resulting in the water being distributed over the full surface of the cloth.

You will just need a double sided tape to stick it to the bottom of the mop cloth bracket and stretch the cloth over it.

It is best printed in TPU to make it conform to the surface even better, but any material will do.