@imnxnyer: Thanks for the bugreport.
I have looked through it, and the reported file really has no use as reported.
The problem is that there is another file duplicati-i8a12d5c9452a46f395af2f070e709cca.dindex.zip.aes that lists what is supposed to be inside duplicati-be27ecf833ff248f78182f2b9fedbeaf3.dblock.zip.aes.
Due to a logic issue in Duplicati, it records the blocks that it finds inside the dindex file , and records these. Then at the check where you see the error, it figures out that these blocks are missing. This is fine, but we should remove unused blocks prior to checking for missing blocks.
For now, there are two ways to fix it.
Simple fix is to remove the file duplicati-i8a12d5c9452a46f395af2f070e709cca.dindex.zip.aes and then rebuild the database.
The other way is a bit more dangerous, but you can open the database with SQLite Browser, and use the “Execute SQL” tab to run this:
DELETE FROM "Block" WHERE "VolumeID" = 3703;
DELETE FROM "RemoteVolume" WHERE "ID" IN (3703, 2813);
DELETE FROM "IndexBlockLink" WHERE "IndexVolumeID" = 2813;
Then remove the duplicati-i8a12d5c9452a46f395af2f070e709cca.dindex.zip.aes and all checks will pass.