Aux Interface Adapter, Rav4 OEM Radio

I have connects2 AUX interface adapter VTYX001 installed to my rav4 original radio

I'm having following problem:
After 10/15 mins or so the sound fades to nothing on all sources. if I turn the ignition off and power off with the key for couple of minutes it will work again for a similar period of time. turning the volume up does not help.

I found from connects2.com forum, that another user had same kind of problem and he had found a solution for it. I just don't understand the solution which he wrote following:

"Have tested a solution witch seems to work:
On the Connect2 box a 4 v DC signal on pin 4 (orange wire) is sensetive and control the main unit speaker output levet. From 4 V DC to 0 the speakers go to low level.
I have mounted a 1 kOhm pull up resistor to +12 V rising the signal to 9 VDC and every things seems to work normal. "

Could someone please explain that to me?