ARSENAL plugin does not load in Logic Pro X (not validating) if not Admin User

Hi community,
my son and I share a MacBook Pro. I am the main user (the Admin) and my son has another user account on it set up. We both are musicians and using Logic Pro X.
We figured out that the ARSENAL VST plugin loads and validates ok under Logic Pro X, if I (the main admin user) is logged on. When my son logs on with his account the ARSENAL plug in is not active. When opening the imbedded Logic PlugIn Manager I can see the ARSENAL plugin cannot be validated. When I try a reset I get in the status windwow the following messages :

validating Audio Unit Arsenal by M-Audio:

AU Validation Tool
Version: 1.6.1a1
Copyright 2003-2013, Apple Inc. All Rights Reserved.
Specify -h (-help) for command options

Manufacturer String: M-Audio
AudioUnit Name: Arsenal
Component Version: 1.0.0 (0x10000)
Component's Bundle Version: 0.0.0

* * PASS
[Symbiosis](0x7fff71690310) AU kComponentOpenSelect
[M-Audio: Arsenal](0x7fff71690310) Found my image (/Library/Audio/Plug-Ins/Components/Arsenal.component/Contents/MacOS/Arsenal) at 113 of 160
[M-Audio: Arsenal](0x7fff71690310) No VST bundle or alias found in resources, assuming fat AU bundle
[M-Audio: Arsenal](0x7fff71690310) Bundle retain count before releasing: 4
[M-Audio: Arsenal](0x7fff71690310) VST open
[M-Audio: Arsenal](0x7fff71690310) VST audioMasterVersion
2015-11-08 19:56:05 0: ZenConfigurationBase::initConsoleLogger()
[M-Audio: Arsenal](0x7fff71690310) VstPluginMain called ok
[M-Audio: Arsenal](0x7fff71690310) Invalid AEffect* returned <<<<<<<<<<<<<
[M-Audio: Arsenal](0x7fff71690310) Exception while opening vst plugin
[M-Audio: Arsenal](0x7fff71690310) Bundle retain count before releasing: 3
[M-Audio: Arsenal](0x7fff71690310) Bundle retain count before releasing: 2
[M-Audio: Arsenal](0x7fff71690310) Caught exception in SymbiosisEntry: VST main() doesn't return object AEffect*
[M-Audio: Arsenal](0x7fff71690310) AU kComponentCloseSelect
FATAL ERROR: OpenAComponent: result: -32767,0xFFFF8001

validation result: Open failed

In my opinion a bug. The error shows up at the point marked with <<<<<<<<<<
Any Ideas ????
1 person has
this problem