The banana split simply acts as parallel THRU ports?
I think we should try to reproduce the issue with a direct MIDI cable to a single port, just to keep reducing the variables and zero in on where the issue is hiding. 
The banana split simply acts as parallel THRU ports?
I think we should try to reproduce the issue with a direct MIDI cable to a single port, just to keep reducing the variables and zero in on where the issue is hiding.