EB3A: Fan ALWAYS on in UPS-mode

Received the replacement for my first EB3A yesterday.
Now UPS-mode seems to work without interruptions … but new challenge ahead:
While in UPS-mode the fan is ALWAYS on and pretty loud as if it were a 2000kWh station charging at max. speed, regardless battery is at 100% and silent charging mode is activated.
Would anybody know how this symptom can be healed?

Please contact our customer service team and provide relevant videos to confirm the fan malfunction. Our customer service team will arrange a replacement for you. Thank you for your cooperation.

Sounds great, thank you!

Most likely you will forward me again to my local reseller who just took back the first unit with a malfunction and sent me this one.

He will not be delighted at all and will be running out of stock if this dilemma keeps on occurring.

My idea was to have a power station available for spontaneous use rather than shipping it to and fro. Sorry for my bitterness.

Any further proposal?