Just got a brand new HX one and having the same problem with midi. Pass through only works when the input channel is set to OMNI. I suspect the fault is that the midi input Channel setting is ingnoring all midi signnals except the channel selected. In my case the HX one is channel 5 and the next unit in the midi chain is set to channel 1. The manual states all midi output is channel 1 but this is not happening ( yes midi thru is set and the Channel 1 unit works connected to the midi contoller, firmware updated). I have not tested if channel 5 is passed through because even if it is it has no utility as chanel 5 is already used.
Unless I have missed something, this appears to be a design fault. If so, it is suprising that Line6 would release a product below their usual high quality standards especially for a simple and well established function like midi thru.
