[rancid] how cisco nx-os switch work with rancid with read-only account

[yuan song]

i have a read access account "RO" in nexus 3048, and i add it to
.cloginrc file like that:
add method 10.36.0.71 {ssh}
add cyphertype * aes128-ctr,aes128-cbc,3des-cbc
add user 10.36.0.71 ro
add password 10.36.0.71 XXX
add noenable 10.36.0.71 1

however, rancid log give me:
10.36.0.71: End of run not found
Error: TIMEOUT reached

But, if i give my account full read&write permission, It works just fine.
Hope someone could help me here, thx a lot

PS:nexus config
role name rancid
rule 1 permit read
rule 2 permit command show *
username ro password XXX role rancid