zfs sync wait 1 hour

Hi to all,
I have strange problem, and that sync waits exactly one hour, and I am not sure why.
There are other VMs on that server that replicates on the exactly same secondary server, and there is no problem there.

2019-05-19 21:00:01 106-1: start replication job
2019-05-19 21:00:01 106-1: guest => VM 106, running => 12890
2019-05-19 21:00:01 106-1: volumes => local-zfs:vm-106-disk-1,local-zfs:vm-106-disk-3
2019-05-19 21:00:03 106-1: freeze guest filesystem
2019-05-19 22:00:03 106-1: create snapshot '__replicate_106-1_1558292401__' on local-zfs:vm-106-disk-1
2019-05-19 22:00:03 106-1: create snapshot '__replicate_106-1_1558292401__' on local-zfs:vm-106-disk-3
2019-05-19 22:00:03 106-1: thaw guest filesystem
2019-05-19 22:00:03 106-1: incremental sync 'local-zfs:vm-106-disk-1' (__replicate_106-1_1558234801__ => __replicate_106-1_1558292401__)
2019-05-19 22:00:04 106-1: rpool/data/vm-106-disk-1@__replicate_106-1_1558234801__ name rpool/data/vm-106-disk-1@__replicate_106-1_1558234801__ -
2019-05-19 22:00:05 106-1: send from @__replicate_106-1_1558234801__ to rpool/data/vm-106-disk-1@__replicate_106-1_1558292401__ estimated size is 1.07G
2019-05-19 22:00:05 106-1: total estimated size is 1.07G
2019-05-19 22:00:05 106-1: TIME SENT SNAPSHOT

 

Yes, guest agent is installed (but it is old windows 2003 server) and service is started. How do I verify if it is working correctly?
Dorijan