You're correct, in that I was the only one in the group using Delayed Overload Cascade, but if you look through the log, all of its uses were on Donatra, the Gates, and the Tac Cubes. It is possible that one of the uses pushed away that last sphere, but no one can say for sure. Donatra was usually away from the spheres, and Delayed Overload Cascade doesn't have that wide of an area of effect (2 kilometres). That last sphere was a sprint away from Donatra's kill spot. It's also possible that the sphere got bumped out by the Neutronic Eddies (which I was also responsible for), or that it was just left behind and wandered off while we were killing Donatra. Looking through the combat log, there was never any damage applied to the spheres and probes (that I could tell from how the log is recorded anyway) by Delayed Overload Cascade, and the last damage reported from Neutronic Eddy, on spheres and probes, was while we were still working on the gates.
(All times are in EDT) At timestamp 16:01:59.4, the final sphere (it wasn't the final sphere yet, but it would end up being the final sphere that caused our problems) engaged you (Distant Knight). At timestamp 16:02:04.9, my final Neutronic Eddy hit Donatra. At timestamp 16:02:05.7, your Hanger Pets engaged the final sphere. At timestamp 16:02:06.3, Miles' pets engaged the final sphere. At timestamp 16:02:41.1, my final Delayed Overload Cascade hit Donatra. At timestamp 16:02:46.3, your Delta Alliance Reinforcements Pets began attacking the final sphere. At timestamp 16:02:48.1, Donatra died, followed by her core breach at 16:02:48.7. At timestamp 16:02:50.0, you began attacking the final sphere with a Fire at Will attack. At 16:02:51.9, my Hanger Pets began attacking the final sphere. At timestamp 16:02:52.6, Pedigo's Hanger Pets began to attack the final sphere. At timestamp 16:02:53.9, my ship came into range of the final sphere and began to attack. At timestamp 16:02:57.0, Solace's ship came into range of the final sphere and began to attack. At timestamp 16:02:57.5, the last record for the final sphere was logged. Throughout this time-frame, from 16:01:59.4 to 16:02:57.5, the final sphere was attacking you. Therefore, it must have been within range of at least you, and since you have a tanky build, I'll assume that it was attacking you because you were holding aggro.
All of this is to say that the sphere in question was in constant contact with you (Distant Knight) and your pets for almost a full minute before Donatra died, all the while going unnoticed by, and/ or out of range of the rest of us, until the very end. I could ask you, what happened???
If you are still paying attention, lol, you're probably right. The last activation of Delayed Overload Cascade probably pushed the final sphere away from us just enough to cause us to fail the mission. I do take special care to try not to scatter mobs, and I thought that Donatra was far enough from everything to not cause a problem. We were running up against the timer, so I was throwing everything that I had available at her! If my actions caused us to fail, and detracted from your enjoyment of this particular TFO, please accept my sincerest, most heartfelt, and humble apology. I will endeavor to do better....after having gotten you to read through this wall of mess, lol!!!
Cheers!!!