This is a native x10 issue
defer all non-critical 2.1.2 issues to 2.2.
Problem is in iterator of the BandedRegion. Since that's a PolyRegion, it probably means that some part of PolyRegion isn't working correctly. Problem is in class library (shows up in either backend).
bug is that Iterator on PolyScanner was relying on hasNext() and next() being called in lockstep because hasNext actually modified the iterator's state to prepare for the next call to next().
fixed in 21273.
bulk close of all 2.2.0 resolved issues.