[SNMP4J] Can you help me work it out?

[ning zheng]

We use SNMP4J in our SNMP management application and we've recently run into an issue 
The issue is as below: (A: net-snmp  B:SNMP4j)

1. A-->B: A send a snmptrap to B with engineBoots and engineTime values with zero. -- send trap (engineId set but engineBoots and engineTime set to 0) 
2. B-->A: NotInTimeWindow Report (engineId, engineBoots, and engineTime set)    
3. A-->B: A re-send the snmptrap with right engineId, engineBoots, and engineTime from B -- send trap (engineId, engineBoots and engineTime set)
4. B-->A: NotInTimeWindow Report (engineId, engineBoots, and engineTime set)
5. Repeat Step 3 and 4 

My question is why B always report NotInTimeWindow(in 4,6,8) even A has set the right engineId, engineBoots and engineTime. 
I check the RFC3414 about NotInTimeWindow, but not found the root cause, seems the trap from A should be accepted. Is there a SNMP4j bug?

Thanks very much for any feedback!
Stephen