i attached 3 screen shot (1-3) from phpMyadmin. The problem is not very often but it certainly is reproducible.
As you see sometimes clock and ns for different events is the same. In result - macroses in notification also the same.
'ns' calculation mechanism should be improved.

The problem arises when an agent reads for example, 10 events and sends them. But it first, it sends one, then pauses (BufferSend 5 sec) and then sends the remaining 9 is single bunch. But after the first event and pause and may be an issue visible.
Perhaps this problem is more reproducible immediately after starting the server, and probably always. Hard for me to say.