Experience the same issue. My phone is 2 monts old!!! The problems started directely after update. I bought the edge version for its battery life. I will never update the OS without reading all the opinions first. The worst thing is that feom what you describe Samsung does not want to acknowledge the problem :
Yes I've noticed that it is all about being on cellular network, particularly where there is a bad signal.
How did you find the process of returning to Nougat; where did you get the instructions, was it reliable and did it take a long time?
I also contacted Samsung support and they were next to useless. They were adamant that it is must be something to do with the phone. They didn't seem to understand or accept the fact that the change was a direct result of the software update. They even said they'd inspect the phone but if there wasn't anything wrong with it there would most likely be a cost to me. A dose of my experience/cynicism says that they're not going to do anything about this problem. I hope I'm wrong on this.
Firstly, just a heads up to anyone with this issue. We strongly advise against flashing your phone yourself. Modifying the phone's software can void your warranty and can prevent access to core apps.
You can report issues such as this through the Samsung Members app. There's a guide on how to do that here. If you're not in the UK, the process may be slightly different so you should raise this with your local Support Team.
If you look further down in this thread (you probably already have) you will see that moderator LiamH has replied about how to access the Samsung Members app to report the issue. I don't know how effective that is having never tried it, but will have a go.
Thanks for the information on downgrading; very helpful. Have you had any problems with it? Apparently you can switch off the constant update notifications in developer options. This might help you. NB. LiamH has said that it's strongly recommended not to do that. But that information from Samsung is to be expected I guess...
This thread has gained a reasonable amount of traction since I posted so hopefully Samsung might realise there's a problem and not try to dismiss it as rogue apps, user incompetence, phone battery as it appears these are default responses.
Thanks for your communication. Hopefully you can see there really is a problem with S7 edge phones and Oreo. This post has gained a reasonable amount of traction in a few days and it's only the people who know to come to the Samsung Community and use the correct search terms and put the effort in to reply / add to the posts. Think about how many other S7 Edge customers there must be out there also with this problem but who haven't found this community forum yet.
As a moderator you must have some authority here which you can use to back us up. I'm happy to have a go at posting directly through the Samsung Members app, but equally since you recommend not flashing phones ourselves I'd recommend in return that you insist that Samsung remove the Oreo update so that more people aren't tempted to do exactly what you're asking them to refrain from. Will you do this?
Interesting information, thank you. I'll try the app anyway. Possibly a rhetorical question for you: when they say display error, do they mean the cell standby or the actual battery percentage, or both? Most of the time the percentages don't add up to 100 either. And my battery drains quicker, and it is warmer to the touch than with Nougat.
In the absence of qualifying answers to these questions it makes me think that either they don't know what they're talking about or are fobbing us off. If Oreo was the problem there would be more than just Samsung people complaining elsewhere but I've seen no evidence to support this. Even some other Samsung phones are fine apparently.
I really don't know what to do about this issue but unless Samsung or a moderator can do something constructive to help, downgrading is a serious possibility for me, despite the rhetoric.