Accumulation of memories that kills.
As a vehicle grows older, their AI Core stores a constantly growing amount of memories. Experiences, knowledge, skills, names, places, .... all the information that a vehicle is exposed to and has to retain to function can normally be handled well by their core. Recalling it is a matter of miliseconds if it was memorized sufficiently. But over the years, all this data piles up. While old information usually gets "purged" periodically during a vehicle's sleep to free up space, this process can be faulty or fail completely for a variety of reasons. Even when running correctly, the process is not perfect and will leave some junk data behind. At some point, the amount of stored information starts slowing down the core's function. It continuously has to sift through millions of pieces of information to recall the desired data. This causes delay, and this delay gets worse and worse until the core completely locks up. Once this happens, it's impossible to break the loop.
A very subtle illness. By the time the effects become noticeable, immediate treatment is needed to prevent the final stage. Overhead is incredibly difficult to spot, since the response delay caused by it only amounts to one or two seconds at most, in its latest stages. This may sound like an insignificant timespan, but is a thousandfold deterioration from healthy response times. The symptoms are easily mistaken for a distracted or "dreamy" mind, or misattributed to just being a "slow thinker". The key to spotting this illness is paying close attention to the individual's behaviour and recognizing changes. If a normally witty tank becomes pensive and frequently dumbfounded, this could be a sign of Overhead.
The only effective treatment for this condition is an extensive memory purge - something that can't be easily conducted. Messing with a core's memory is risky, and the available means of doing so are crude. The "treatment" consists of inducing artificial, partial amnesia. This is achieved by effectively hacking into the core's memory and deleting large chunks of whatever data there is. The success rate of this operation is a matter of perspective - while the total lockdown is prevented by it in the majority of cases, it may leave the patient distressed and/or alienated from their surroundings due to the severe memory loss. In some cases, the deletion causes significant changes in personality or renders a patient unable to perform basic tasks; some recover from this by re-learning what went missing, while others can't function normally anymore.
- Chronic, Acquired