The problem with the crash due to wifi traffic had been resolved in the revision 2644 for uTrack. Any version you have beyond this should not have the crash due to wifi.
Coming to your other question about the reliability, we have done tests with upto 4 devices connected to the same uTrack. We have not found any problems. But again, we have not done long term testing with 4 devices connected to the same uTrack.
We can safely tell you that with 2 devices you should have no problems at all with the reliability.