Cosmos DB Change Feed Processor distribution of traffic to multiple instances in the same deployment unit doesn't seem to work

I am using the .NET SDK V3 (3.26.0) for Cosmos DB.

According to the documentation, Cosmos DB Feed Change Processor should distribute traffic in parallel to multiple instances in the same deployment unit (same processor name and leasing container).

I have been trying to do that, running three (and more) instances, but only one instance receives calls, the others remain idle.

When the receiving instance is stopped, I would expect that another instance picks up almost immediately, instead several seconds (30-60) pass before another instance begins receiving messages

Questions:

1. How can we ensure that the feed change processor distributes calls to multiple active instances in the same deployment unit?
2. How can we ensure that the feed change processor switches over to other active instances quickly when an instance stops?
3. What happens if an instance crashes without calling StopAsync?