With the latest batch of EX Raid Battle invites, we implemented a few changes to improve Trainer and Gym selection. Unfortunately, a bug was introduced when these changes were made, and, as a result, some Trainers were invited to participate in an EX Raid Battle at a Gym they may not have visited in several months. This bug has already been resolved, and future invites will better represent how the updated invitation process is intended to function. Most importantly, Trainers will only receive an invitation if they’ve completed a Raid Battle at that Gym recently.
We've also made a couple changes that will impact the invitation process. First, we've made changes to the ways Gyms are selected. While EX Raid Battles will continue to take place in parks and at sponsored locations, the number of Gyms that meet the necessary criteria for an EX Raid Battle will increase. Additionally, the average number of Trainers invited per Gym will also rise, as we've made a few tweaks to the way they are selected. Thanks to these two changes, more Trainers will have the opportunity to engage with the EX Raid Battle feature.
The quality of EX Raid Battles at these locations should also improve. To start, Trainers with a higher level Gym Badge are now even more likely to receive an invitation for an EX Raid Battle at that location. Similarly, Trainers who complete more Raid Battles (at any location) the week before EX Raid Battle invitations are sent will now have a greater chance of being selected.
We appreciate the feedback many of you have shared over the past several weeks and apologize for any frustration the latest batch of invitations may have caused. We're constantly monitoring feedback shared on various social media and support channels, so please continue to share your thoughts on your preferred channel as we continue to fine-tune this feature.
—The Pokémon GO team