Having too many online applications open at once can crash the system Settings app of your device running Android 8.0 Oreo, with some users recently experiencing the issue after migrating to the latest major iteration of Google's mobile operating system. The bug itself seems to not discriminate against any particular handset as a number of owners of the Pixel, Pixel XL, and some Nexus devices have all reported Settings crashes under certain conditions. The system app only appears to be unstable when users try to access their mobile or Wi-Fi data usage metrics, with this section of the app apparently rendering itself but immediately causing a crash accompanied by the operating system's generic "Settings has stopped" message.
The problem was originally recorded by one of Xiaomi's engineers in early March, as evidenced by its listing in the Android Issue Tracker which can be accessed by following the banner below. Reproducing it in Android 8.0 Oreo should be as simple as opening a large number of online apps and trying to access the mobile or Wi-Fi data usage stats, i.e. the "DataUsageList" of the OS. The exact number of applications that need to be open for Settings to crash has yet to be disclosed, though the issue itself was apparently already fixed in early April, but the relevant code has yet to make its way to the Android Open Source Project master branch, which is also evidenced by the commit linked below. The author of the fix from Xiaomi does note that the code failed some basic debugging tests which a Google reviewer later attributed to "unrelated flakiness" and approved the fix. The current state of affairs indicates that a patch resolving the issue may be distributed in the near future and users affected by the problem are advised to manually close some of their online apps in the meantime if they want to access their Internet data usage graphs.
At least one user claims that the same issue was also present on the Nexus 5X running an unspecified build of Android Nougat, noting how the transition to Android 8.0 Oreo actually resolved it, though the apparent cause of the bug suggests that their device may still be prone to crashes and simply wasn't running enough online apps when they tested it following the Oreo update. Another user seemingly managed to prevent the mobile data usage graph from crashing by changing the start date of its cycle, though the same method cannot be applied to the Wi-Fi usage section of the app seeing how the start of its tracking period cannot be manually set.