While we have history of transaction failures, and the failed screenshot / HTML available, we don't have access to the history of the last "good" screenshot or HTML. When an outage is underway, it would be helpful to compare the last known good state to the current bad state. It would only require 1 last good entry per step, whereas right now we keep multiple last bad entries per step, so this would add only a fraction of the storage, yet give us a really valuable reference during an outage.
