Unexpected side effects of using slice append
When slicing another slice, the newly created slice will have a pointer referencing the backing array of the original slice. This means that any modifications to either slice will be reflected in both.
Mistake
When appending contents to either slice that will not fit inside the backing array, a new backing array must be created. This breaks the relationship between the two slices.
Fix
Create a copy of the original slice to avoid this behavior.