The problem occurs when an additional MetaIndex structure is added to an index. If you try to retrieve your structure, it seems to load always the default MetaIndex, with only one key: "docno". This happens because the word "meta" is taken as the name of the structure by default in the class CompressingMetaIndex.
|Status||Open [ 1 ]||Patch Available [ 10000 ]|
|Status||Patch Available [ 10000 ]||Open [ 1 ]|
|Status||Open [ 1 ]||Resolved [ 5 ]|
|Fix Version/s||3.1 [ 10040 ]|
|Resolution||Fixed [ 1 ]|