Syncrepl loosing synchronization

Hi all,
  I have 6 servers which all synchronize with syncrepl mechanism from
  a single master.

Of that six server one is the master and 2 are local connected servers,
every server is a 2.4, plus there are 3 remote connected servers which
are all 2.3

With local connected i mean LAN (maybe different DMZ) while remote
connected i mean WAN (with data over the relative-slow link).

It happens frequently that the remote servers loose synchronization
with the master (no more updates to data) when/if the link goes down.
Or even when the link is slower the usual.

The local connected servers are all with refreshAndPersist while the
remotes one are refreshOnly.

Every replica has a retry of "60 +" so it tries indefinitely and the
refreshOnly ones has an interval of 45


Did you have any clues while is should loose synchronization and the
only possible solution is to rebuild the whoile DIT on the replicas?

Cheers
-- 
Massimo