Xperia 1 II loses 4G connection in Telenor Bulgaria's network

[peter_sl]

Hello,

I've been using Xperia 1 II (XQ-AT51) for about 3 months and I keep experiencing severe network issues with Bulgaria's Telenor mobile network operator. When I'm outside of urban areas, the handset shows it is connected to 4G, but when I try to use data it immediately disconnects and displays "No coverage" for a few seconds. Afterwards, it reconnects, but it only lasts until I attempt to use data again. This cycle continues infinitely, regardless of whether I'm moving or staying still. The preferred networks setting is set to 4G/3G/2G and if I change it to 3G/2G, I don't experience the problem. Other phones in the same area don't have any network issues. You can watch a screen recording of the handset's behaviour here.

And here comes the curious part: when I go to Software Info in the Service Menu (*#*#7378423#*#* > Service Info > Software Info) I see that the Current Modem Config is Telenor_Sweden.

This is totally incorrect in my opinion and probably has much to do with the network problems of the phone, because Telenor Bulgaria does not use the same set of 4G frequency bands as Telenor Sweden, which renders the handset unable to find the frequencies it expects. If I put a SIM card of another Bulgarian operator (A1, Bulsatcom) into the phone, the Current Modem Config changes to ROW_Commercial.

I'm reluctant to take this to a service center, because as I mentioned above, this happens only outside of urban areas, and will not be reproducible at all in the city where the service center is. I'd like to hear some opinions about my theory that the wrong modem configuration is causing the network issues, as well as how you think this can be corrected. I'm guessing it would need Sony to fix the software wrongly identifying Telenor Bulgaria's SIM card as Telenor Sweden one.

Thank you,

Petar

[Poseng1]

Got my android 11 and testing

[Poseng1]

I bought mine in Hong Kong and also had the android 11 update yesterday. It did seem to have fixed the 4g internet problem for me. I didn't have a single drop since the update. I really don't know how to help you. Factory reset is the only thing to try

[EMS_MO72]

Try to force restart your device after the update and check again, sometimes there are glitches that happen after the update.

[math.el]

After updated to Android, I restarted many times, reset factory, reinsert
SIM card and more.

[Poseng1]

This is the version 58.1.A.1.178 I have for dual sim. If it's the same and you still can't connect then you should take it for repair or wait for another update. Most of us don't have problem after android 11

[peter_sl]

It might be worth testing SIM-cards by different network providers and noting the current modem config for each one, as well as whether there are network problems or not. Sharing your results here could be useful to Sony engineers for resolving these issues, if they follow the topic at all. 

[EMS_MO72]

Try to contact Sony regarding this matter to send your device for repair if the troubleshooting steps didn't work.