Can't access subdir from top dir even as a root user

[JaneSoo]

I mounted the bucket from S3 with the following command
sudo goofys -o allow_other mybucket /mnt/buckets/mybucket/

inside mybucket, there are a bunch of subdirectories.

When I do rsync or cp (with sudo) some subdirectories, I ran into a problem:
sudo cp -rv /mnt/buckets/mybucket/a /destination
cp: cannot access '/mnt/buckets/mybucket/a/b/c': Input/output error

sudo rsync -arv --delete /mnt/buckets/mybucket/a /destination
rsync: [sender] readdir("/mnt/buckets/mybucket/a/b/c"): Input/output error (5)
IO error encountered -- skipping file deletion

however, if I copy or rsync full path sudo cp -rv /mnt/buckets/mybucket/a/b/c /destination there was no problem at all.

I did ls -al, all directories and subdirectories have all permissions for root and other user

when I did ls -al /mnt/buckets/mybucket/a/b/c first time, I got this error:
ls: reading directory '/mnt/buckets/mybucket/a/b/c': Input/output error

but after I kept running the same command, I finally saw all the directories and files under it.

Does anyone know what could be the problem?