When used in the context of a PEAR, FSArrays internally store the "base" version of a feature structure for their elements. When accessing the elements e.g. via the get(i), method, this "base" version is converted to the proper version for the given PEAR context on access.
However, the FSArray.spliterator() method does not perform this conversion and directly returns the "base" versions.
The toArray(...) method is also affected by the problem.