Does this mean you get different error or no error if another version of AIX is running.

It sounds as an issue with RPC communication between server and client. Did you have that with previous NW version or is this new install?

Exactly the same error on the other AIX clients.

These clients used to have version 7.2 installed. They were upgraded to 7.4SP3 and
moved to a new backup server.

Could be anything then. Try to play with rpcinfo to see if you get anything strange. Also, try to put some other NW version on AIX client to see if it makes any difference.

Is your version of AIX supported with NW 7.4 version that you are using?

Hary, they have 5.3 - that's supported.

The thing is that rpcinfo in both ways (i.e. from the server to client and from client to server) is working 100% with no strange output at all.

There is no reason (that I can see) why this should not be working...

Sorry ... my mistake ... didn't notice the AIX version ...

Is it possible that name resolution is making some funny tricks here? Like you start save and then server resolves client IP to something else giving different RPC response then expected.

Aahhh! I feel like an idiot!

Typo in the hosts file!

Thanks for all the input!