[zymhan]

When you're floating along on a stable orbit not about to impact the surface.

Or with more time to recover from the outage before landing. If it happens within the last minute (wild estimation) then you have little time to recover the lost velocity.

[Hamuko]

But you're still having an engine failure when the engine is far away from anyone that could potentially start mending it.

[Jach]

Not an engine failure, but: "Debugging a program running on a $100M piece of hardware that is 100 million miles away is an interesting experience." http://www.flownet.com/gat/jpl-lisp.html

[zymhan]

"failure" does not necessarily imply it is permanently disabled. It just means the engine stopped working as expected at some point.

Obviously they restarted it after this failure so it was not a complete breakdown of the engine.

[sailingparrot]

When you are floating along on a stable orbit the engines are off, so it's quite hard to have a failure in this context.

[ses1984]

Maybe the failure occurs as you are initiating acceleration burn, while you are in stable orbit.

[nkrisc]

They could fail to ignite if you were attempting a burn from a stable orbit into another orbit.