Automower-fans

Hello!
Sorry for my question in english, but my french is non-existant
I have this mower for 4 years and last 2 years it has started to go left and right when following the wire. Anyone know the possible reason and solution for this problem?
The working area is the maximun(7000m2+) and the wire lenght is about 1,5km, but the bases station gives no errors and the robot dose not lose the signal, thats why i think that the wire length is not the problem.
Attached is a video of the roboto going home
https://youtu.be/WPJAkaCKvvc

Bonjour / Hello.
- une possibilité: n'avez vous pas placé un cable électrique enterré à ces endroits /Did you ever placed any electrical wires buried in these areas?
- autre possibilité: axe de rotation et roulement d'une roue avant est faussé / axle and ball bearing damaged or stuck in one of the front wheel .