I made a wireshark capture on a test system today. The request / response packages look ok to me. There was a request package for every unmatched response. There were no error messages in the log.
The unmatched responses happen much more often on the production systems, maybe the phenomenon is load related.
07:12:59 Response 15713
Request 15719
07:13:10 Response 15714
Request 15721
07:13:20 Respone 15717
Request 15723
07:13:37 Request 15726
07:13:41 Response 15719
Response 15721
Request 15727
07:13:58 Request 15730
07:14:05 Response 15723
07:14:11 Response 15726
Request 15732
```
```
INFO | jvm 1 | 2018/06/14 07:13:41 | W [o.e.m.o.s.c.UaTcpStackClient ] [05:13:41]: Received unmatched PublishResponse with requestHandle=15719, timestamp=DateTime{utcTime=131734340257232072, javaDate=Thu Jun 14 09:13:45 CEST 2018}
INFO | jvm 1 | 2018/06/14 07:14:05 | W [o.e.m.o.s.c.UaTcpStackClient ] [05:14:05]: Received unmatched PublishResponse with requestHandle=15723, timestamp=DateTime{utcTime=131734340499458170, javaDate=Thu Jun 14 09:14:09 CEST 2018}
INFO | jvm 1 | 2018/06/14 07:14:23 | W [o.e.m.o.s.c.UaTcpStackClient ] [05:14:23]: Received unmatched PublishResponse with requestHandle=15727, timestamp=DateTime{utcTime=131734340683166396, javaDate=Thu Jun 14 09:14:28 CEST 2018}
2018-06-16-OPC-UA.zip (43.1 KB)