Kessil a160 gremlins

[Aquariumaddictuk]

Good evening all

A bit of technical advice required if possible!

I recently sold 3 kessil a160we units on ebay after upgrading to orphek atlanktik.

All 3 cleaned and working fine.
Buyer has claimed an issue with one light, specifically

*fan Continuing to run when light is off
*very loud humming during operation

Chap seems genuine & hasn't asked for a refund more advice really.
A video is incoming showing light noise.

I ran two lights off the kessil controller & had one running on a simple smart plug.
New buyer says he has all 3 running off the controller so I don't know if that could cause an issue, electrics are not my thing.any input would be useful, I'm aware I'm not giving a huge amount to go off

 

[Aquariumaddictuk]

Received video
Fan is going full speed absolutely flying which makes me think its a voltage issue.
When power banks switched its still doing it toi