I've seen MIDI-OX mess up handling of sysex dumps - from my Behringer DeepMind 6.? Bome's SendSX worked perfectly.
I seem to have read somewhere that Windows MIDI drivers expand "running status" - so that software receives entire self contained MIDI messages instead of a status message followed by a stream of values for it.? If it was receiving a sysex dump but didn't see the header, for example, it could then mangle the data considerably, thinking some of it was running status messages, and adding the extra status bytes.
I've had success using JSynthLib with my TX7, so I'd try that, to see if it can receive a dump from your DX7:
but first try Bome's Send SX because it's simpler, with much less of a learning curve:
Maybe just connect the DX7 direct to the PC via your no name USB-MIDI cable?? I'm not familiar with the MOTU but it sounds complicated enough to be part of the problem.
- Andy
AndyHornBlower