Ok, after testing for few days, here is my experience in an area very populated of radio stations with RDS:

empeg chages frequency withour staying on the same station, every few seconds, in an urban area where no frequency change should actually occur since each station has only ONE frequency in the whole area. So, in my case, the freqeuency chage actually occured only to a different station.

What's new since my last post is that this time I verified that the problem occurs both using a preset and after changing frequency back and forth with the remote control to simulate manual tuning, as Prolux suggested. I have tested this tens of times for few days.

When activating the AF debug mode, I see that the frequency/station change occurs each time any frequency other than the one I'm listening gets stronger.