Mirror of Master 2.4 and slave 2.3: slave silently exits(0)

I've set up 2 slapd in mirror mode. All worked fine until some moment. 

Now slave server exists(0) just after start and sync. Master is 2.4,
slave is 2.3. During sync there are alot of "bdb_search: ## does not
match filter" log entries. What may cause this?

Last lines on slave:

bdb_search: 92 does not match filter 
send_ldap_result: conn=-1 op=0 p=0 

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Покотиленко Костик <[email protected]>