Had it happen last night twice and now today.
All three times not doing PVP but exploring Kingdoms.
You know the error message so I don't think including another picture is going to help. But boy this is weird.
I hadn't seen this in months, then to have it happen three times in the last 24 hours + the Weekly PVP has ended message as well = something's triggering the wrong messages with the servers.
Also this is even weirder - The next game (again Kingdom explore) is the same set of troops (I noticed this last night and shrugged it off - teach me to be a normal consumer instead of my QA engineering hat). I don't know if that helps. And yes it is the identical team since I hadn't seen one of the troops before fully traited I walked through them all.