Recently, I was leveling up a friendly gym right after i had taken one down. After several battles, the gym would not let me battle anymore and it would say error. The next day i would be able to battle the same gym with no problem. I think i have heard of people being soft banned form gyms recently, but i don't know why this happens or for how long. Would you guys know anything about this?
Happens due to gps drifting causing a 15 minute ban.
Here's how to avoid it.
Go go to the gym. Choose all your Pokemon. When you press fight, turn off your GPS/Location services.
The game just locks you at the place you were standing for the entire battle and you will not get that error (from GPS drift) at all.
