As per a post on the forums, a member was having an issue where raiders were ticking too slowly.

After doing some testing, I came up to the conclusion that the raiders' activation range is being overridden by the monsters' activation range.

When setting my values to this:

    entity-activation-range:
      raiders: 100
      animals: 100
      monsters: 1
      misc: 100
      tick-inactive-villagers: true

A raider should be ticking within the 100 block radius, but standing anywhere within this range, raiders were barely moving. I stood about 2 blocks away, still nothing! The raider wouldn't move until I was standing right next to him.