When Pokemon GO first launched last summer, the servers just couldn’t keep up with demand and they were also hit by a DDoS attack. But although developer Niantic managed to get the game over these humps, its hit mobile game is not invulnerable to other server issues that prevent would-be Pokemon Trainers from playing the game.

The latest problem with Pokemon GO‘s servers occurred yesterday when a huge amount of players reported that they were unable to log-in to the game. According to data from Down Detector, 64% of Pokemon GO players on both iOS and Android said that they experienced log-in problems yesterday while 35% of players complained about server connection issues. The issue also seemed to affect players with Google Accounts as well as those with Pokemon Trainer accounts, suggesting that it was a Pokemon GO issue and not a Pokemon Trainer or Google-related problem.

Fortunately for upset players, Niantic soon posted an update confirming that it has been looking into the issue. Four hours later, the developer announced that it had “resolved” the issues preventing players from logging into Pokemon GO, with Niantic also thanking everybody for their patience.

Niantic didn’t detail exactly what the problem was – such as whether it was due to high server demand – but some fans are concerned. This is not the first time that the game has experienced server-side issues this month, with the release of the special Ash Hat Pikachu being delayed because of technical issues. Although Niantic was quick to act in this case too, the fact that it didn’t go smoothly in the first place is raising some eyebrows.

This summer is set to be huge for Pokemon GO, with events like the Pokemon GO Fest taking place just next week. The interest surrounding the real-world festivities are set to increase the number of active users even more, adding to the strain that the game’s servers are already under. It could spell disaster if Niantic is not prepared.

Moreover, Niantic is said to be testing Pokemon GO legendary Raids in some locations and the release of legendary Pokemon is (potentially) right around the corner. Once introduced, these will be some of the biggest updates in the game’s history and, again, a massive influx in players is to be expected. If these new features have rocky launches, many players are going to be upset, so hopefully Niantic will focus to ensure that all goes right.

Pokemon GO is available on iOS and Android.