Fallingbrook, Chapel Hill and Convent Glen have plenty of interlock that has been through twenty or more winters. Frost heave at the front steps and joints washed out on sloped walkways are common.
Avalon and Notting Hill are newer, with wide driveways that show low spots quickly once the base settles. Repairs, re-sanding and sealing are done in the same visit where the base allows it.
Lift the sunken or heaved section, fix the base, relay the same pavers and compact them level.
Full excavation, a compacted granular base built for Ottawa frost, and pavers rated for vehicle traffic.
Clean out failed joints, refill with polymeric sand, and seal if you want colour and stain protection.
Rebuild leaning block walls and loose interlock steps with a proper footing and drainage behind them.