Watching the OBiAPP > Properties > Status > Call State during calls and checking in your OBi202 Web Page > Status > Call History after calls may give useful information here.
If you dial **9222222222 from your softphone to get the OBi echo test, you will see that the call goes from the softphone to the OBiAPP then straight to the Obihai servers. Your OBi202 is not involved. The OBiAPP is an independant "endpoint".
If you dial from your softphone to a number that matches your Primary Line DigitMap (default sp1), then the call will be set up via OBiAPP and the Obihai servers and you will see in the OBI202 Call History the call has come in on the OBiTALK network and gone out on sp1. However, when the call is answered, the OBi202 can see that the softphone and sp1 are in the same subnet, so it will connect the RTP (speech) paths together locally and not via the OBiTALK network. This means that my first reply to you was probably not helpful.
Check to see that the calls that fail are routing correctly on the right sp1, sp2 etc the same as calls from the OBi Phone Port are routing. If all the routing is corect, then it may be that the X-Lite is not receiving something that it needs. You might try another free softphone like 3CX to prove it one way or another. 3CX setup examples are on this forum if you do a search.