M-Audio Oxygen 25 problems

Since updating Logic Pro to 10.2.3 I have had serious problems using my 3rd Generation Oxygen 25 keyboard/controller which I never had before.

Problems

1: the keyboard simply doesn't produce any sound anymore OR no input signal is detected

2. if connected and recognized, the keyboard produces stuck sounds when testing new sounds (as if there was no Turn Off recognition)

Note: the keyboard is a USB class recognized device (so no extra drivers)

What I've tried so far:

- Rebooting the Mac Book Pro

- Deleting Audio Devices Cache

- Resetting all MIDI settings and devices

- Deleting and re-installing Logic Pro

What I've discovered so far:

- if recognized, the keyboard turns up in the control part of Logic (and e.g. transport control, works fine, so the problem is limited to musical notes)

- If GarageBand is started before Logic, everything works fine. The minute I start Logic after that, the keyboard stops working in GarageBand

- If I then kill both apps and restart GarageBand, the keyboard no longer produces sound (i.e. once Logic has been used, it's dead to other apps)

- Starting the MIDI monitor program after a reboot and before either music program shows MIDI events work fine (all parameters, incl. Turn Off). If I then start Logic, the program no longer sees the keyboard.

Summary:

If I start Logic, it removes the visibility of the keyboard in other programs and they cease to see the device/data sent.

I would be really grateful for any tips/advice and I'd like to know if anyone else has this or similar problems.

FYI: Mac OS: El Capitan 10.11.5