> archive(0, 0x4d385643): cannot find block: error reading block 0x0021cac2 > archWalk 0x4d385643 failed; ptr is in 0x2075 offset 3
0x4d385643 is supposedly a block number, which seems unlikely unless you have a >10 terabyte disk. Looks like you have a VtEntry or pointer block with a corrupted score (to be precise, entry 3 in block 0x2075), but in this case it should be the score for a local (fossil) block, not a venti block.
