Both were fine for awhile, which could also just be due to not compacting some bug-causing file. Potentially there are other bug-causing files around, but to find them would mean big download.
SharpCompress has indeed been updated since 2.0.8.1, but I couldn’t see announced changes making potential problems of compatibility with the old version. You can tell when your suspect dblock files were made from the file date (maybe) or from the Each dblock file has a manifest giving Created time and Duplicati AppVersion.
Google search site:forum.duplicati.com “LZMA” “Data error” “zip.aes” led to two reports in 2018.
SharpCompress.Compressors.LZMA.DataErrorException
SharpCompress.Compressors.LZMA.DataErrorException: Data Error
It looks like the SharpCompress message comes from actual file extractions, so just reading the names of the files (which is possibly all some operations do) might not be enough. Another idea:
Duplicati.CommandLine.RecoveryTool.exe
you can use the Recovery Tool to convert your backup files to another compression type.
This would force reads of the LZMA files (so maybe fail) while changing compression to Deflate.
Duplicati.CommandLine.RecoveryTool.exe recompress zip “C:\tmp\recompress.pre” “C:\tmp\recompress.post”
is what I just tried, with .pre folder having a dblock file from an LZMA backup. I can confirm compression method in 7-Zip. The .post file got Deflate. You can test copies of bad dblocks.
Unfortunately, new ZIP code in 2.0.9.108 chokes, so you might need a 2.0.9.107 .zip install.
1/1: duplicati-b0a69695168d443dfa437b9d44b6de54e.dblock.zip - downloading (773 bytes)... recompressing ... error: System.IO.InvalidDataException: The archive entry was compressed using LZMA and is not supported.
at System.IO.Compression.ZipArchiveEntry.Open()
at Duplicati.Library.Compression.ZipCompression.BuiltinZipArchive.OpenRead(String file)
at Duplicati.Library.Compression.ZipCompression.FileArchiveZip.OpenRead(String file)
at Duplicati.CommandLine.RecoveryTool.Recompress.Run(List`1 args, Dictionary`2 options, IFilter filter)
Another technique which I haven’t tried yet is an open source GUI tool using SharpCompress.
SimpleZIP (Microsoft page, and it’s also in Microsoft Store, if for some reason you prefer that).