The problem becomes harder when proving a pattern matters more than changing the next occurrence.

Building a case and solving a problem pull in opposite directions. Once the goal is establishing that this always happens, every new instance becomes useful as evidence, and there is a quiet incentive to let it recur so the point can be made. Meanwhile the other person is defending their record rather than thinking about next Tuesday, and nothing actually changes.

Drop the history for one conversation and aim at the next occurrence only. Ask what would need to be different on that specific coming occasion, and treat that as the entire subject.