I have installed Zabbix 3.0.18 on Ubuntu 16.04. I am using "zabbix_trap_receiver.pl" to handle my traps and I have configured the file this way:

/etc/snmp/snmptt.conf

EVENT general .* "General Event" Normal
FORMAT ZBXTRAP $aA $aA severity: $s $Fn + $*

 

which is following Zabbix trap format:
[timestamp] [the trap, part 1] ZBXTRAP [address] [the trap, part 2] 

When I send traps via IPv4/IPv6 with SNMPv2 I can see the trap in Zabbix properly

2018-07-05 15:26:30		
15:26:29 2018/07/05 PDU INFO:
  receivedfrom                   UDP/IPv6: [2607:f160:a:f0:9:fe0:0:2000]:1096
  errorindex                     0
  messageid                      0
  community                      public
  notificationtype               TRAP
  transactionid                  18
  errorstatus                    0
  requestid                      0
  version                        0
VARBINDS:
  .1.3.6.1.2.1.1.3.0             type=67 value=Timeticks: (23993228) 2 days, 18:38:52.28
  .1.3.6.1.6.3.1.1.4.1.0         type=6  value=OID: .1.3.6.1.4.1.232.0.11003
  .1.3.6.1.2.1.1.5.0             type=4  value=STRING: "TXSLPERFLAB-H-PE0C7O1-001"
  .1.3.6.1.4.1.232.11.2.11.1     type=2  value=INTEGER: 4
  .1.3.6.1.4.1.232.11.2.8.1      type=4  value=STRING: "HPE Onboard Administrator Test Trap sent from enclosure: TXSLPERFLAB-001"
  .1.3.6.1.6.3.18.1.3.0          type=64 value=IpAddress: 192.168.80.33
  .1.3.6.1.6.3.18.1.4.0          type=4  value=STRING: "public"
  .1.3.6.1.6.3.1.1.4.3.0         type=6  value=OID: .1.3.6.1.4.1.232
  
  
 Problem occurs when I use IPv6 with SMPv3 the Zabbix trap info get cut off in the middle see below 2 traps (picture attached):
  
 2018-07-05 15:34:38		
15:34:37 2018/07/05 PDU INFO:
  requestid                      783365081
  version  
  3
  
2018-07-05 15:24:20		
15:24:18 2018/07/05 PDU INFO:
  securitymodel                  3
  messageid                      807769804
  errorindex                     0
  receivedfrom                   UDP/IPv6: [2607:f160:a:f0:9:fe0:0:2002]:1234
  securityName                   zabbix
  securitylevel                  3
  contextName
  

  
  
  
  
Comparing with the "/tmp/zabbix_traps.tmp" output I see some garbage characters randomly inserted see red highights:
  
  15:34:37 2018/07/05 ZBXTRAP 2607:f160:a:f0:9:fe0:0:2002
PDU INFO:
  requestid                      783365081
  version                        3
  securityEngineID               <80>^@^@^K^D74:46:a0:f9:d9:70
  notificationtype               TRAP
  errorstatus                    0
  transactionid                  20
  contextEngineID                <80>^@^@^K^D74:46:a0:f9:d9:70
  securitymodel                  3
  messageid                      807769806
  securityName                   zabbix
  securitylevel                  3
  receivedfrom                   UDP/IPv6: [2607:f160:a:f0:9:fe0:0:2002]:1234
  errorindex                     0
  contextName                    
VARBINDS:
  .1.3.6.1.2.1.1.3.0             type=67 value=Timeticks: (24039431) 2 days, 18:46:34.31
  .1.3.6.1.6.3.1.1.4.1.0         type=6  value=OID: .1.3.6.1.4.1.232.0.11003
  .1.3.6.1.2.1.1.5.0             type=4  value=STRING: "TXSLPERFLAB-H-PE0C7O1-002"
  .1.3.6.1.4.1.232.11.2.11.1     type=2  value=INTEGER: 4
  .1.3.6.1.4.1.232.11.2.8.1      type=4  value=STRING: "HPE Onboard Administrator Test Trap sent from enclosure: TXSLPERFLAB-002"
  .1.3.6.1.6.3.1.1.4.3.0         type=6  value=OID: .1.3.6.1.4.1.232
  
  
  15:24:18 2018/07/05 ZBXTRAP 2607:f160:a:f0:9:fe0:0:2002
PDU INFO:
  securitymodel                  3
  messageid                      807769804
  errorindex                     0
  receivedfrom                   UDP/IPv6: [2607:f160:a:f0:9:fe0:0:2002]:1234
  securityName                   zabbix
  securitylevel                  3
  contextName                    
  securityEngineID               <80>^@^@^K^D74:46:a0:f9:d9:70
  version                        3
  requestid                      783365079
  transactionid                  17
  errorstatus                    0
  notificationtype               TRAP
  contextEngineID                <80>^@^@^K^D74:46:a0:f9:d9:70
VARBINDS:
  .1.3.6.1.2.1.1.3.0             type=67 value=Timeticks: (23977577) 2 days, 18:36:15.77
  .1.3.6.1.6.3.1.1.4.1.0         type=6  value=OID: .1.3.6.1.4.1.232.0.11003
  .1.3.6.1.2.1.1.5.0             type=4  value=STRING: "TXSLPERFLAB-H-PE0C7O1-002"
  .1.3.6.1.4.1.232.11.2.11.1     type=2  value=INTEGER: 4
  .1.3.6.1.4.1.232.11.2.8.1      type=4  value=STRING: "HPE Onboard Administrator Test Trap sent from enclosure: TXSLPERFLAB-002"
  .1.3.6.1.6.3.1.1.4.3.0         type=6  value=OID: .1.3.6.1.4.1.232