Stalling slave transfers

[Tom Sommer]

Hi,

I have a problem with one of 3 slave servers, all set up the exact same 
way, with the exact same bind version and configuration.

One slave has a problem transfering zones from the master.

The logfiles are flooded with "received notify for zone" .. "refresh in 
progress, refresh check queued" lines and "rndc status" returns a 
constant high number of "soa queries in progress".
After a few hours the zones are transfers, so the connection to the 
master is working, but there is a major delay. I tried resetting the 
slave and transfering ALL slave zones again, which worked fine 
instantly. The problem still appeared again after a few hours though.

The master has three network-paths, one on external IP, one on internal 
IP and one on IPv6. All 3 paths work fine, because the transfers happen 
after an hour or so.

There is no hints in the master's log.
The other two slaves are running perfectly, no errors or delays what so 
ever.

Bind version 9.9.2-P2 (recently upgraded to).

Any hints would be appreciated, as I feel like I've exhausted most 
options.

Thank you.
-- 
Tom Sommer