Hanging notes on stop when also sending clock to midi ports

Cubase
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1

Has anyone experienced something similar as described here?

System:

  • MacBook Air M2 16GB macOS Tahoe 26.3.1
  • Cubase 15.0.10
  • Motu Midi Express 128 midi interface with latest drivers 1.6 7cf7f5397
  • Motu 828 (2024) with latest firmware and drivers

Steps to reproduce:

  • Create an External instrument linked to midi device that uses Express 128 Port 1
  • Project sychronisation setup → MIDI Clock Destinations → Express 128 Port 1 ticked
  • Add track with above External instrument
  • Add midi event, say 4 four bars, with several notes in it and loop this
  • Hit play and stop, this results in hanging notes regardless of the connected midi instrument (happens with synths from different brands built from 1995 to 2025, and midi cables of different lengths).

This also happens on Express 128 Port 2 to 8. This does not happen when not sending midi clock. This test case runs flawlessly in Cubase 14 and with equivalent setups in Logic 12 and Live 12.

Workaround:

  • Save Project
  • while cubase is not running: disconnect the Midi Express 128 from usb
  • In the MacOS Audio Midi Configuration Utility remove Midi Express 128
  • Physically reconnect Midi Express 128
  • Load project
  • Fix missing midi port mappings
  • Repeat test, no hanging notes

Quit and restart Cubase more than once and the hanging notes issue is back.

While this does not happen in Cubase 14 and also does not happen in Cubase 15 with instruments that connect directly with usb, I’m on the fence on whether this is a Motu, Cubase or MacOs issue. Any help or insights on this will be much appreciated.

2

I’ve done some additional testing, using Snoize midi monitor and feeding the midi output back in to a midi input. In Cubase 14 on a stop the last messages send are a note off and a stop (FC). These are both received at the midi input port. In Cubase 15 there are also a note off and a stop message send, but only the stop message is showing up at the input port. This is really puzzling me. The time between sending the note off and the stop message seems to be a tiny bit shorter in Cubase 15 than in Cubase 14. Perhaps something has changed between Cubase 14 and 15 in the way the program is communicating with the midi api/driver, but this is only speculation from my side.