PepVPN Test Configuration

When I run the PepVPN Test Configuration using the default 4 streams, I recently get the following error:
“Error: Stream 3: Cannot start connection”

My Balance 210 is configured with 2 WAN wireless LTE connections and uses Pepfusion Solo VPN whose performance has degraded the last month.

When I select 2 streams the test does not kick out an error.

I note that the test comments indicates using more streams in high latency situations.

I do believe that one of the WAN connections has an issue with signal path obstruction (tree leaves which I will rectify in the future) so I am assuming this is the cause of this error but I would like to know more about the what a stream is and does a failed stream correlate to signal “quality”. Should I be happy with a failed stream when doing a 4 stream test or accepting a 2 stream test?

I was not able to find good documentation on this.