Volume drop problem

[Ago]

Hi there!

I have a TI2 keyboard since 2 years now, and since about 1 month - she waited for the summer - she sometimes throw down the output volume.
Here's an audio recording of it (WAV, 48 kHz): soundcloud.com/agostino-anselmo/virus-volume-drop
After a bit that I'm playing a preset (or modifying it as well), the volume just drops down as you can hear: sometimes it comes back up, but immediately drops down again. If I switch to another preset, sometimes the volume stays down, but usually it re-starts at the normal volume, and after a bit it falls back again.

The volume is set to maximum, if it can help. I use it with Windows 8.1 64-bit and Ableton Live 9, but it does it even with just the power cord and headphones plugged in. The same problem comes out of both headphones and master output. And, as you can hear, USB output too.

I already resetted it.

Does anybody know a way of fixing this?

Thank you so much! Have a good day