Integrated changes input selection by itself


Hello. My MF A3.5 has started changing it's input selection to Tuner ALL BY ITSELF. It does this intermittently. I have only two inputs connected, CD and Aux1. There is no other source for the amp to play, yet it switches to Tuner every once in a while. It plays normally, and then jumps to the Tuner input. I then select the Aux1 or CD input with no effect other than I missed a few bars of Jazz. Everything else seems to be normal.

I've had the amp for several years now, and purchased it as a demo from an Audiogon member. This behavior of self-selecting to the Tuner input is a very recent phenomenon.

Here's my system: http://forum.audiogon.com/cgi-bin/fr.pl?vevol&1187457873&view. I've traded up to the Quintet for power filtering and upgraded the speaker wires to Kimber 8PR, all last year.

I could not find any posts with this issue so I'm asking this community for comments and suggestions. Thanks.
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I just power cycled the unit and covered the IR port on the front with a post-it note. Just waiting to see if this works...
An electronics designer told me that sometimes AC filters can boost the line voltage a little bit to make them sound better... but if your line voltage is already on the high side (mine is) the extra boost can cause op-amps to bug-out.

Instead of plugging your integrated amp into the AC filter, try plugging it directly into the wall and see if that eliminates the auto-switching. If not, then it might be time to send it in for service as Tvad mentioned.
Thanks for the suggestions. Since re-cycling power, the unit has not changed input selections. I still have the IR port covered too but I plan to remove that if I the good behavior continues.