Incorrect MIDI messages usb controller (Linnstrument)

[Rampoina]

Hello,

I bought this midi controller: http://www.rogerlinndesign.com/linnstrument.html and I'm having problems with it.
It's detected without any issues and it sends notes correctly but once in a while it sends 2 notes at once (causing one of them to be stuck).
It works correctly on windows and mac without any drivers (it should be class-compliant MIDI over USB).

This is an example captured with aseqdump and just tapping one key:

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Source  Event                  Ch  Data
  0:1   Port subscribed            129:0 -> 130:0
 20:0   Pitch bend              3, value 0
 20:0   Note on                 3, note 57, velocity 57
 20:0   Note on                 3, note 104, velocity 63
 20:0   Control change          3, controller 74, value 86
 20:0   Control change          3, controller 74, value 99
 20:0   Pitch bend              3, value 0
 20:0   Control change          3, controller 74, value 108
 20:0   Pitch bend              3, value 48
 20:0   Control change          3, controller 74, value 113
 20:0   Polyphonic aftertouch   3, note 57, value 46
 20:0   Pitch bend              3, value 120
 20:0   Control change          3, controller 74, value 114
 20:0   Polyphonic aftertouch   3, note 57, value 30
 20:0   Note off                3, note 57, velocity 64
 20:0   Polyphonic aftertouch   3, note 57, value 0

You can see 2 notes being sent.

I've determined that this issue happens a lot more when the y control is enabled (it sends tons of CC 74 messages for every key), they claim that my PC is being overloaded with midi messages but I don't really think that's the case.
My specs are as follow:

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CPU : Intel Quad Core q9550 2.83Ghz
RAM: 4GB RAM

I've also tried it on a laptop with Windows that is considerably less powerful than my machine and it worked (although the laptop had problems generating the sounds with ZynAddSubFx sometimes)
Maybe it's a timing issue?

I'm using Arch linux and a real time kernel. (besides setting the CPU governors to maximum performance, using rtirq and all the other tweaks I could find to make audio work better)
I can use jack with periods/buffer = 2, sample rate = 48000 and frames/period as low as 64 without getting xruns.

I'd really like to solve this and not have to use Windows just to play the instrument but I don't know where to start.
If you could point me out to the resources I need to be able to debug this it would be much appreciated.

[gimmeapill]

Interesting device
What are your settings when it comes to midi? alsa midi might have trouble handling the volume of messages...
According to the Ardour manual, the top dog configuration should be a2jmidid + jack2 - maybe worth a shot?
http://manual.ardour.org/setting-up-you ... -on-linux/