Hi msiwek,
I am suspecting that your two way replica might be in an out-of-synch situation here.
Could you please check the message generation numbers from both parent and child database?
Right click your database connection, Distributed Geodatabase > Manage Replicas, then double click the two-way replica, goto the Advanced tab, then please list your generation numbers like following:
Parent:
Current Generation 1,
Last Acknowledged Generation 1,
Relative Replica Genration 2
Child:
Current Generation 2,
Last Acknowledged Generation 2,
Relative Replica Genration 1
Thanks,
Ben L.