I looked at the first 2 calls ( 526374/1, 8136328/10 ) and in both cases there is an active call and recording session active when call observer is added. Since recording started before call observer is added you will not see a recording start event.
OK.
I'm curious, where in the log files can you tell that i've added an observer after the recording start event?
CiscoTermConnRecordingTargetInfoEv indicates that this is an active recording session and you see a recording end event.
I didn't recieve CiscoTermConnRecordingTargetInfoEv from JTapi

for calls in question (526374/1, 8136328/10),
in InternalLogWithCucmJTapiEvents.log you can see which events i did recieve.
Recording start event will be seen if recording starts after the call observer is added.
it seems that you are adding observer on the call. This is in addition to the call observer on the address/terminal. Call events will be delivered to all the call observers, so application may see multiple events depending on how the call observers are handled. I did not see any issues with the events.
OK.
Thanks for the quick reply.