Status 48 every day

Something is contaminating my Master Server host cache.  All but one client backup fails with Status 48. 

Ran this test:

bptestbpcd -client xxxx

Function ConnectToBPCD (xxxx) failed: 48

client hostname could not be found

so I do this:

bpclntcmd -clear_host_cache

then it works as it should:

bptestbpcd -client xxxx

<ip>.<port> -> <ip>.<port>

But a few hours later it fails again.  DNS entries verified, no problem there.

I can still ssh to the clients by name, ping them, even telnet on port 1556, but bpcd fails until the host cache is cleared again.