THRU-16 Virtual Outputs 4 and 5 Not Working Correctly + Other Issues

Hi, I'm experiencing a critical issue with the THRU-16's virtual outputs 4 and 5, as well as a small issue with outputs 9-16.

The device has been in use for about 8 months, and I only noticed the problem recently because I had not previously needed to use outputs 4 and 5. The behavior is:

• Virtual OUT 1, 2, 3, 6, 7 and 8 work normally, with the THRU-16 activity LED blinking when MIDI is sent.
• Virtual OUT 9-16 also transmit MIDI correctly, although the activity LED does not blink for these outputs.
• Virtual OUT 4 and 5 do not transmit MIDI normally. There is no activity LED indication and no MIDI output. I can sometimes get an initial message, but then it seems to freeze.

Interestingly, in MIDI-OX, if both OUT 4 and OUT 5 are selected simultaneously under MIDI Devices, they can transmit MIDI normally and the activity LED also blinks. However, this workaround does not work with other applications such as my DAWs (REAPER, Cubase) or Stream Deck.

I have reproduced the exact same behavior on two different Windows 11 Pro computers, including a computer with virtually no other MIDI devices installed, so the issue does not appear to be related to my Windows/MIDI environment.

I have also:

• Performed a Factory Reset using MIDI Stream Config v2.0.1.
• Tested with all other MIDI devices disconnected.
• Confirmed that all 16 physical MIDI outputs work correctly when receiving MIDI through the THRU-16's physical MIDI input.

So, in summary:

• Virtual OUT 4 and 5: do not work normally via USB MIDI.
• Virtual OUT 9–16: transmit MIDI correctly, but there is no activity LED indication.
• Virtual OUT 1, 2, 3, 6, 7 and 8: work normally.

Could this be a known issue with the THRU-16 firmware? Is there a firmware update or fix available?

Thank you.

ps. below is a screenshot of MIDI Stream Config. Nothing is filtered.