This has been in Gems of War since 2015!!!
Get rid of this!!
How can this battle ALREADY been finished??? How is another battle already started???
GoW is not Co-Op nor is it a TRUE Multiplayer, we all have our own games that we are playing, HOW CAN THIS GET MIXED UP???!!
THERE IS NO REASON THIS SHOULD EXIST!
Wow now; simmer down now. 
I understand your frustration but it’s not like the dev’s are putting in error codes for the lolz.
The reason the game must communicate with the servers is to ensure people aren’t cheating. If the game was entirely local (ie. no server check-ins) it would be super easy for cheaters to hack the game and get massive amounts of any resource. By keeping rewards and things like that server side, it makes it much harder to cheat and much easier to catch cheaters when they do cheat.
True, the downside is that occasionally we get these types of error messages (usually when the servers get overloaded and communication gets lost between your device and the server) but it is much, much better than the alternative. The game would be literally unplayable if it weren’t for these safe guards. 
The answer is simple, you can start a battle on another device, which causes the game to auto end any open battles.
This is correct but that is not the only reason this error occurs.
I have to agree with the OP on this, I hate wasting sometimes 10-15 minutes on a battle and then get this message.
If this is to prevent someone from hacking or cheating it is probably frustrating the normal users more than the hackers. When playing on 1 device and this error appears, and we just “wasted” our time.
This error should be looked at more, and seriously rethought. I usually end up quitting from the game for awhile after I feel I wasted time and lost my progress.
All you have to do is take a few minutes to report it and you will be compensated.
It really doesn’t happen that frequently to me that I consider it a major problem.
I am all for anything that prevents cheating having recently had a player join my guild and subsequently banned for botting.
No you won’t. The single traitstone and 2-3k gold is irrelevant (and making a ticket to get those back is a waste of time). This bug is a win-streak breaker and no one will ever “compensate” you for that, or give you the win-streak back.
This error is precisely why I don’t give a rats ass about the win-streak anymore. I can try to scout and use different teams to min-max my win chances to keep the streak going, but why bother? If eventually (and at a point that is impossible to predict), you’ll just get this error and all the effort goes “bye”. People say the game gets boring, yeah well this is one of the reasons. I can just faceroll with one team and accept the occasional loss because I don’t care about the win streak. At least thanks to that, when I get this error (yet again) my effort and time won’t go down the drain.
I find the token mismatch error far more frustrating as I have to ctrl alt delete close the game.
And I gotta tell you @AeroCloud if you are spending 10-15 minutes on a battle, you need to revise your army.
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I have been compensated with trophies, glory and gold so I guess if you don’t care about those then don’t waste your time reporting.
The support team is very supportive
I’m not saying every battle takes 10-15 minutes, but there are many occasions where it will because of that last troop wont die. I have learned to simply avoid those teams which also makes me want to play the game less.
I am not in a major guild, I lead my own guild because of friends and family that play on occasions. This gives me less keys/troops and makes my journey much harder than others. I’m sure there are more people in my shoes vs the top guilds, and I’m sure its a frustrating experience for them.
Just because What I’m saying doesn’t align with how you feel doesn’t mean what I’m saying has no value. Please try to look at it from every side, not just your own.
I also dislike the token mismatch as well… anything that makes me feel like I wasted time, makes me want to do whatever wasted my time a lot less.
I didn’t intend to indicate what you said had no value.
Just trying to help you out here.
I apologize if you took it the wrong way.
+1 to this.
The issue isn’t that we have this control: we absolutely should.
The issue is the frequency of errors - which is enough to be annoying even to the most dedicated.
How often are you actually getting these errors and what device(s) are you getting them on?
I ask because other than during the early Monday madness or when GoW is experiencing actual server issues, I rarely see them. It’s always a bit of a kick in the butt when it happens but it’s sounding like you and some of the others must be experiencing them much more frequently than I. Maybe you just play a lot more frequently? I only do a few hundred battles most weeks so maybe that’s it?
Lately the messages have not been as often, maybe a few times a day.
But about 2 weeks ago, it was as much as 5-6 times per hour, and upwards of 50+ times a day.
Playing on both Steam and Android Samsung Note
Hmm yeah, I only see them about once a week at most. Strange. I mostly play on iOS though; I wonder if it has anything to do with that (I kind of doubt it, though).
I play on Android and except as oGunther mentioned, rarely get them
Saw this a few times over the weekend. It does not end your win streak since I’m still around 190 game win streak after seeing it a few times.
I think it happens when servers are busy and it forgets you are playing a battle.
I have to disagree. I got one at the end of last week and it marked my battle as an invade loss and broke my streak. 
It does end for mine to.