Peeling tile grout?

[Ironside]

Hello,

We have noticed that the grout has started to flake in a couple of spots in the bathroom (less exposed areas):



The bathroom is surely 10 years old now, even if it feels fairly modern. What could this be due to? Has additional grout been applied afterward?

 

[Jonatan79]

Yes, or too much tile adhesive has been applied, making the grout too thin and it comes loose