I set up sprinting with a slot in the animGraph, now I can't seem to get any new animation montages to work

You shouldn’t cache your slot animation in that manner, I suspect the issue would happen as a result of being unable to use multiple slot animations at once and the cache already having one applied prevents another from functioning.

It should look like:

  1. Default Locomotion → Locomotion Cache

  2. Use cached pose ‘Locomotion Cache’ → Slot ‘RunSlot’ → Slot ‘dodgeRollSlot’ → Final Animation Pose