One way to fix this would be to revert:
f58ffb26aeaae0642a149643672fa59ec01a3a36
1476d5348fcf387e7481d833becbd993d91f8019
These patches simplified the entryUSN fitler from (&(entryUSN >=
$last)(entryUSN != $last)) to (entryUSN >= $last + 1). This was
requested by Thierry to improve filter-evaluation performance so I
choose to keep this filter and move the incremental logic into parsing
function, appending "Z" or whatever we string remains to the new value
in case of modifyTimestamp attribute.