@EnricoQ, the bright pixel, or pinprick of light, is a common problem across all Kobo models, and is caused by a screen defect; I think it's dust under the glass or something similar. It can't be fixed. So, if you're still in the period in which you are entitled to a return (I see you are in the EU, so that should help), get an exchange.
Kobo really needs to correct their manufacturing procedure and quality control in this area. It's been a problem since the sidelighting was introduced and is an issue across all models.
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