Earlier this week, Apple seeded the seventh developer betas of its next major operating system updates, including iOS 12, macOS Mojave, watchOS 5, and tvOS 12. Later that day, the firm removed iOS 12 beta 7 from its servers, presumably because of stability issues.
Today, Apple released iOS 12 developer beta 8, which should fix whatever issues were present in beta 7 that caused its abrupt removal. There are only a few resolved issues listed for build 16A5357b, such as apps taking longer to launch and Settings crashing in Speech settings. None of the resolved issues should have been a reason for the build being pulled earlier this week.
One thing that is notable is that group FaceTime calling was removed in beta 7, and that should come back in a future update this fall.
Development of these major updates should be in its final stretch. There might be one more beta build in a week or two, and then there will be a final GM seed after Apple announced new iPhones in early September. Following that, the public release of all four feature updates will be toward the end of the month.