Mindrot

The most common illness of the AI Core. As it ages, it becomes faulty to the point of failing completely. The machines call this process "Mindrot". No one is safe from the condition - every machine can develop it, and it is strongly believed that, given they live long enough without dying from other causes, every machine will develop it.
Once it has set in, the illness advances fast. Some sufferers last one or two more years, but most die within a few months.

Causes

Other than with other illnesses, the causes for this one have been pinpointed pretty precisely - it doesn't take a genius to figure out that at some point, an AI core simply starts degrading. Since they are always in use for every second of a machine's life, they eventually amass errors and the components fall apart until it finally shuts down.
Thus, Mindrot technically has two causes, leading to three "types" of the illness. Type 1 Mindrot is the failure of only the neurologic components. Type 2 Mindrot is the sole failure of the mechanical components. Type 3 Mindrot, the most severe type, is the simultaneous failure of both. All three types lead to the sufferer's death, but Type 3 is thought to do so the quickest.

Symptoms

Mindrot is easy to spot once it has developed far enough that the sufferer starts displaying symptoms. By then, it is safe to say that the affected machine does not have much time left. It starts out subtle - increasing forgetfulness may be a sign, as is irritability or a loss of drive. Sufferers in the early stages may feel constantly exhausted or restless, or alternating between the two.
In the later stages, the illness shows itself in paranoia and depressive episodes or bouts of anger and hostility, which are amplified by increasing loss of short-term and long-term memory.
The machine may lose their sense of sight, direction, hearing. They might need assistance with the easiest tasks such as refueling or using their weapons. Panic attacks become frequent.
In the final stages, conscious thought becomes increasingly impossible. The sufferer loses all autonomy, becomes completely dependent on others - they act in irrational ways, lose all sense of time - what happens now is as present as the past to them; seconds may become eternities or hours may pass without notice. The ability of coherent speech is lost. At some point, they practically enter a vegetative state.
The next, terminal stage is death.
What we know about the symptoms stems mostly from outsider observation of the affected individuals. Very few sufferers are able to express themselves about their state once the symptoms set in. Those who are able are often in fierce denial.

Treatment

There is no treatment for this condition, as it is a creeping mechanical/neurological breakdown.

Prognosis

Every known case of Mindrot eventually led to the sufferer's death. Everyone is aware of this, and while some sufferers hold the frail hope that one day their condition may be treatable - before it is too late for them - a lot of vehicles have made it their will to have their comrades kill them when they display the telltale signs of the illness. This is because due to the nature of it, affected machines might not be able to put an end to their own suffering; when the memory loss or mental state becomes severe enough, they stop being aware of their condition and become bogged down in their slow, inevitable deterioration.

Prevention

Impossible to prevent, since it is the result of wear of the core. "Miraculous cures" are simply a rip-off by quacks.

Epidemiology

Typically, older machines start falling victim to Mindrot. According to estimates and studies, the risk increases with advancing age, and is thought to peak at about 90 years. Most sufferers are about 70 to 80 years old. Technically however, machines of any age can be affected. Some fall victim to it at a very young age already, though not nearly as commonly as older ones.

Type

Neurological

Cycle

Chronic, Acquired

Rarity

Common