Pavements are usually made of paving slabs

Not where we live. I can only think of one street where the pavement is slabbed and walking down there is a bit hazardous.

At our old house the footpath crossing (which we paid the council to construct after we bought the house) sank over the years (probably no more than a inch) but even with the Caterham there was never a hint of grounding the car. It was certainly more of a risk to pedestrians and I raised it with the local Councillor when he came begging for our vote. Nothing was ever done but other roads in the district where members from that part lived (not a party that has any members in government) were resurfaced at some considerable expense.

Not what you know etc.

If it's adopted, report it to the relevant council. Any damage it causes can then be claimed if it's not repaired within a reasonable time.

I don't know what 'reasonable' means.

Normally they only fix road and pavement issues if they are of imminent danger. A large pothole in the road, especially where to avoid to is either impossible or you have to swerve into oncoming traffic would be a good example. For pavements, it normally is either a large, deep hole or severely broken surface, mainly because young children, the elderly or disabled could easily trip and fall, and also get badly cut/injured by the sharp debris.

I make sure any report gives such information as it then ups the priority to a 2-day job. It does work, at least for the 'better-run' councils' highways depts. Most non-critical work gets put into a long queue, which could be weeks or even months to get repaired.

Always best to be honest about the report, and include photos where possible. A wrongly categorised fault can lead to serious injury - case in point a local road gully collapsed, leaving a hole, but filled up with water, and a kid fell through. Needless to say after it was publicised in the local rage, the council fixed it the next day.