WiFi Repeater It.Works, unstable connection

Hello,

I bought an It.Works N300 wifi repeater in a store. I think it was 29.99 euros, the cheapest one offered.

We asked the salesperson who said that if he were us, he wouldn't buy it because at that price it surely wasn't good quality and he recommended others. We still went for the It.Works, the cheapest, because if it's on sale, it should work in theory.

I should have been cautious; on the shelf, there were already 2 It.Works repeaters like the one I bought that were customer returns; you could tell the boxes were open and taped. I took one that was sealed. And here we have a problem: when we connect to the repeater via Wifi, we are regularly disconnected automatically without doing anything special. I've already tried changing the wifi channel from the box, I also reset the repeater and went through the installation again, but nothing works; when we are connected to the repeater via wifi, it's unstable.

When we connect directly to the box via wifi, it's very stable regardless of the device used. The internet connection where the repeater is located is very good; I checked it with my phone and my computer by standing right in front of the repeater. However, I need the repeater to extend the wifi network further. What can we do? I really don't want to buy a 60 euro repeater; it's expensive...

Thank you in advance