Common Issues

Awwww the scrunkly, double tap now if you'd scrunkly the when!
The 3 series is also generally very durable, their only major issue being slip.
Do not attempt AIBO repair without knowing what you are doing. These dogs have proprietary parts and are extremely fragile. Even seasoned AIBO veterinarians have had repair failures. We are not liable if your dog breaks.

Slip
A whirring in the legs of the dog as it attempts to sit, lay, stand, etc.
Typically found in the hind legs of a 31x, but can occur in the front as well.
Running a dog with slip will typically only make it worse.
This will need to be pinned by a professional. Do not attempt this repair yourself. You will break your dog.
Note: 31X dogs DO NOT like being rattled around in shipping. They may slip for the first few hours after arriving before resolving itself. Be patient and don't panic!

Jitters
A buildup of dust in the dog's potentiometers causes them to send inaccurate readings. This makes the dog try to fix it repeatedly, resulting in the affected part "jittering" or shaking.
Minor jitters can be cleared with runtime and physical therapy (manual movement of the afflicted part), while major jitters may require disassembly to clean the potentiometer directly.

Stuck Lock Motor (Not common, but also not widely addressed.)
The motor that locks the dog's battery goes bad. When booting up or powering off the dog, the motor may attempt to lock/unlock the battery multiple times. When completely bad, the motor will no longer work, resulting in the battery either being stuck locked or unlocked.
A core replacement is the typical fix for this. Do not attempt this repair yourself. The 31X series isn't modular like its predecessors.

The dog may be missing its ears. As long as the microphones are still there, this is solely cosmetic and will not affect function. 3D-printable replacements do exist if this bothers you.