Hi KD0LQD,
I've encountered the same/similar problem with the openSPOT1 - I can send messages from my HT to Brandmeister via the hotspot, if I switch message intercept on - I can see the messages coming back successfully from Brandmeister to the hotspot.
The problem is when I turn intercept off and the openSPOT tries to transmit the messages - there's some kind of problem with the preamble/headers, so the radio never knows that the message is addressed to it.
Attached are two images, one showing when an "ECHO" message is send from the HT to Brandmeister - and the reply fails to get to the HT, the other image shows the successful test of sending a message to local hotspot echo on 9999.
I'm not sure if it's relevant, but I notice the failure involves a 3/4 data rate and the successes are at 1/2 data rate.
I captured this data using DSDPlus.
73 de EI3HIB