A testcase to reproduce the issue is attached.
2. enter some data into field 'input2' and field 'item' (field item is surrounded by ui:repeat) and leave the first field 'input' empty
3. click button
result: validation error and field value of field 'input2' is shown (this is expected). But field value of field 'item' is not shown anymore (this is not expected)
Note: with mojarra-2.1.5 the field value doesn't disappear