Bugs
During a charge animation, if the game doesn't have the images for characters cached, the game soft locks. This is (probably) due to the game process the animation faster than it could cache the textures (due to a slow internet connection or server stress), causing it to try to shrink empty textures. The devs could avoid this by implementing a universal missing texture (such as the pink checkerboard Source uses) as a placeholder for missing assets. As for a temporary hot fix right now, the end user could slow down the game speed (either by the in-battle option, or for cease usage of game tuning apps that reduce the internal rendering resolution to reduce frame time).
This issue seemed to be fixed through a change in how animations are played, as well as predownloading assets before the start of phase 1.
Web Page Soft Lock
On Android, locking your device or swapping apps while a web page is loaded in-app (such as an event or a gacha list) will cause the page to be unable to close, requiring relaunching the app.