pdfizeopt doesn't recognize /Filter/Fl in <</Filter/Fl/First 24/Length 102/N 4/Type/ObjStm>>stream. It should recognize it as /Filter/FlateDecode. Also /Filter/A85 ahould be recognized ad /Filter/ASCII85Decode.
There are some PDFs in the wild which have abbreviated filter names. They are not valid PDF, so pdfsizeopt should unabbreviate the filter names.
% Contrary to the published PDF (1.3) specification, Acrobat Reader
% accepts abbreviated filter names everywhere, not just for in-line images,
% and some applications (notably htmldoc) rely on this.
/unabbrevfilterdict mark
/AHx /ASCIIHexDecode /A85 /ASCII85Decode /CCF /CCITTFaxDecode
/DCT /DCTDecode /Fl /FlateDecode /LZW /LZWDecode /RL /RunLengthDecode
pdfizeopt doesn't recognize
/Filter/Flin<</Filter/Fl/First 24/Length 102/N 4/Type/ObjStm>>stream. It should recognize it as/Filter/FlateDecode. Also/Filter/A85ahould be recognized ad/Filter/ASCII85Decode.There are some PDFs in the wild which have abbreviated filter names. They are not valid PDF, so pdfsizeopt should unabbreviate the filter names.