Btrfs, checksum corruption

I have Btrfs setup on 3 disks with metadata and data in RAID1. But now I have a checksum error which it cannot recover. The checksum is the same on both copies and only differs from the expected checksum by one flipped bit. Therefore I suspect there was a bitflip on the checksum before it was written to the disks (the computer does not have ECC RAM). I have a copy of the actual file on another computer from before it was written to this filesystem but as shown below I cannot read out the data due to I/O error from the filesystem so I cannot compare them. How should I go on to fix this error? Some details: $ uname -a Linux stan 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux $ btrfs --version btrfs-progs v4.15.1 $ sudo btrfs fi usage /media/btrfs/ Overall: Device size: 7.28TiB Device allocated: 3.91TiB Device unallocated: 3.36TiB Device missing: 0.00B Used: 3.83TiB Free (estimated): 1.72TiB (min: 1.72TiB) Data ratio: 2.00 Metadata ratio: 2.00 Global reserve: 512.00MiB (used: 0.00B) Data,RAID1: Size:1.95TiB, Used:1.91TiB /dev/sdb 1.95TiB /dev/sdc 998.00GiB /dev/sdd 1001.00GiB Metadata,RAID1: Size:4.00GiB, Used:2.63GiB /dev/sdb 4.00GiB /dev/sdc 3.00GiB /dev/sdd 1.00GiB System,RAID1: Size:64.00MiB, Used:304.00KiB /dev/sdb 64.00MiB /dev/sdc 64.00MiB Unallocated: /dev/sdb 1.68TiB /dev/sdc 861.95GiB /dev/sdd 861.02GiB Scrub: $ sudo btrfs scrub status /media/btrfs/ scrub status for xxxxxx scrub started at Mon Aug 24 11:23:27 2020 and finished after 03:41:54 total bytes scrubbed: 3.81TiB with 2 errors error details: csum=2 corrected errors: 0, uncorrectable errors: 2, unverified errors: 0 Dmesg error after scrub. $ dmesg ... 196755.786038] BTRFS warning (device sdb): checksum error at logical 3099310968832 on dev /dev/sdb, physical 1300730499072, root 5223, inod e 6521311, offset 7614464, length 4096, links 1 (path: users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2) [196755.786168] BTRFS warning (device sdb): checksum error at logical 3099310968832 on dev /dev/sdb, physical 1300730499072, root 5303, inod e 6521311, offset 7614464, length 4096, links 1 (path: users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2) [196755.786245] BTRFS warning (device sdb): checksum error at logical 3099310968832 on dev /dev/sdb, physical 1300730499072, root 5302, inod e 6521311, offset 7614464, length 4096, links 1 (path: users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2) ... [196755.788274] BTRFS error (device sdb): bdev /dev/sdb errs: wr 0, rd 0, flush 0, corrupt 2, gen 0 [196755.814044] BTRFS error (device sdb): unable to fixup (regular) error at logical 3099310968832 on dev /dev/sdb Inspect-internal on block: $ sudo btrfs inspect-internal logical-resolve -v 3099310968832 /media/btrfs/ ioctl ret=0, total_size=4096, bytes_left=3456, bytes_missing=0, cnt=78, missed=0 ioctl ret=0, bytes_left=4023, bytes_missing=0, cnt=1, missed=0 /media/btrfs//snapshots/stansafe.20200601T032501+0200/users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2 ioctl ret=0, bytes_left=4023, bytes_missing=0, cnt=1, missed=0 /media/btrfs//snapshots/stansafe.20200910T032501+0200/users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2 ioctl ret=0, bytes_left=4023, bytes_missing=0, cnt=1, missed=0 /media/btrfs//snapshots/stansafe.20200909T032502+0200/users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2 ... Trying to verify the file: $ sha256sum /media/btrfs//stansafe/users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2 sha256sum: /media/btrfs//stansafe/users/joachim/Bilder/Canon/270CANON/IMG_7003.CR2: Input/output error $ dmesg ... [1642985.509498] BTRFS warning (device sdb): csum failed root 259 ino 6521311 off 7614464 csum 0x151ad4ce expected csum 0x150ad4ce mirror 1 [1642985.509942] BTRFS warning (device sdb): csum failed root 259 ino 6521311 off 7614464 csum 0x151ad4ce expected csum 0x150ad4ce mirror 2