I'm a little bit scared about it as well and I'm unsure of what we can do to further mitigate that risk. I modified pushBackToScheduled to allow for the caller to specify whether they want it rescheduled at the top or the bottom of the ordering. For this type of failure we push to the bottom of the ordering, so that having two (two because locatorFetchConcurrency == 2) persistently bad slots would not block other slots from getting rolled (other than child slots of those slots).

We should figure out a better way to deal with that scenario