Bafang BBS02 issue battery

[Fri287]

Hi, my bbs02 750w worked perfectly until recently. Now I cannot switch it on and realised that the battery goes in security mode when switched on! The battery worka perfectly on an other bike and I checked the power wirering until the motor which has no issue. On this I estimate that the issue is with the engine then.

Anyone has had such an issue and could help me finding a fix?

Regards,