USB MIDI device crashes when connected to second device

Question

Using my Ubuntu laptop I'm trying to connect these two MIDI devices together:

• Device 1: USB-MIDI connection
• Device 2: Standard 5-pin DIN connector with el cheapo USB-MIDI cable

Observations...

• Both devices are recognised when I query with aconnect -i
• When connected individually I can see that midi data is being sent to the PC using aseqdump ip command
• When both are connected Device 2 goes a little haywire: midi timing is all over the place and when I play notes it triggers random midi events
• I can connect both devices together using aconnect port1 port2 with some success i.e. notes/clock are sent/received but, as above, the timing is all over the place and the notes being received are not those being sent

Is there any reason why these devices would function correctly when used individually but conflict with each other when plugged together?

n.b. I've actually got the same results when using Ubuntu 16.04 and with a Raspberry pi3 (running Raspbian Stretch).

Is there any way I can trouble shoot this further? I've not had much luck searching the forums.

EDIT

Outputs of lsusb, amidi -l and dmesg below: lsusb Bus 002 Device 002: ID 8087:8000 Intel Corp. Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 002: ID 8087:8008 Intel Corp. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 003 Device 002: ID 8087:07da Intel Corp. Bus 003 Device 007: ID fc02:0101
Bus 003 Device 006: ID 2367:0004
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

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amidi -l IO hw:2,0,0 OP-1 Midi Device MIDI 1 IO hw:3,0,0 USB MIDI Interface MIDI 1 n.b. 'OP-1' is the device using usb-midi natively; the USB MIDI Interface is the usb-midi:din cable I bougth

dmesg [ 160.384595] usb 3-3: new high-speed USB device number 3 using xhci_hcd [ 160.514100] usb 3-3: New USB device found, idVendor=2367, idProduct=0004 [ 160.514104] usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [ 160.514106] usb 3-3: Product: OP-1 Midi Device [ 160.514108] usb 3-3: Manufacturer: Teenage Engineering AB [ 160.514109] usb 3-3: SerialNumber: ba0cee833ba00000f0800a3b6baf452a [ 160.528907] usbcore: registered new interface driver snd-usb-audio [ 167.813095] usb 3-2: new low-speed USB device number 4 using xhci_hcd [ 172.927641] usb 3-2: device descriptor read/64, error -110 [ 188.149899] usb 3-2: device descriptor read/64, error -110 [ 188.365965] usb 3-2: new low-speed USB device number 5 using xhci_hcd [ 193.479687] usb 3-2: device descriptor read/64, error -110 [ 209.311930] usb 3-3: USB disconnect, device number 3 [ 209.679951] usb 3-1: new high-speed USB device number 6 using xhci_hcd [ 209.808712] usb 3-1: New USB device found, idVendor=2367, idProduct=0004 [ 209.808715] usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [ 209.808716] usb 3-1: Product: OP-1 Midi Device [ 209.808717] usb 3-1: Manufacturer: Teenage Engineering AB [ 209.808718] usb 3-1: SerialNumber: ba0cee833ba00000f0800a3b6baf452a [ 489.157137] usb 3-2: new full-speed USB device number 7 using xhci_hcd [ 489.286966] usb 3-2: New USB device found, idVendor=fc02, idProduct=0101 [ 489.286970] usb 3-2: New USB device strings: Mfr=0, Product=2, SerialNumber=0 [ 489.286972] usb 3-2: Product: USB MIDI Interface

Answer 1

I know this is way later, but: I see something similar with USB MIDI when one of my stations sends MIDI clock -- it's like some of the other non-realtime messages get "stuck" in the buffer and are retransmitted every now and then. But it's totally unsystematic.

Turning off clock transmit at the source, and then disconnect/reconnect USB devices, makes the problem go away.