If some unsafe code gets interrupted by a panic when it's in an intermediate state (before it can clean something up, or make two values consistent), then further operations on that state can result in UB. See https://github.com/becheran/grid/issues/19, https://gitlab.com/tspiteri/rug/-/issues/47, and https://gitlab.com/tspiteri/rug/-/issues/49 for a few of the less-contrived issues I've filed.

It can also result in logic errors if objects are used after their methods panic, but such usage is generally not expected to work in the first place.