WIFI problem on new iPhone 8?

Question

iPhone

Good luck, gentlemen. I need your help. Bought recently (about 2-3 weeks ago) two iPhone 8. American and European. So, now we noticed that the European has problems with WIFI, when the screen is locked, after 1-2 minutes the WIFI icon disappears and WIFI does, after unlocking it comes to its senses in 2-3 seconds, and sometimes even after 10-15, and in very In rare cases, it thinks for so long that it is easier and faster to manually turn it off and on in the WIFI settings. I turned off Autoconnect and Autologin in the network settings, it helped for a while. But I can’t arrange dances with a tambourine every time I connect to the network? I'll notice! That on the second gadget pah-pah, everything is stable, nothing is turned off. This brings inconvenience and quite an irritable feeling, if you immediately open it in the browser - then it sends due to the lack of a network, sit, wait until it thinks. There can be no problems in the router, it was the same at home and in the same way now on a rented hut (two different routers, two different providers, on the second gadget I will repeat in both cases - everything is fine). Network settings - reset. Gadgets were purchased in a cellular communication salon, punched through IMEI, everything is clean. I plan to come - to go to the salon, to understand. My suspicions lie down that it could be a factory marriage? I certainly don’t want my brand new smartphone to be disassembled and repaired by grenade due to the fact that I was already sold with a defect. Can you tell me if the problem is something else? I plan to come - to go to the salon, to understand. My suspicions lie down that it could be a factory marriage? I certainly don’t want my brand new smartphone to be disassembled and repaired by grenade due to the fact that I was already sold with a defect. Can you tell me if the problem is something else? I plan to come - to go to the salon, to understand. My suspicions lie down that it could be a factory marriage? I certainly don’t want my brand new smartphone to be disassembled and repaired by grenade due to the fact that I was already sold with a defect. Can you tell me if the problem is something else?
PS And even notifications do not come! Really a nightmare =(