clarion rd3-01 pu-2471a- broken FM function?

Hi,
I have a Clarion RD3-01 HU on my Peugeot 206. After Immo Off I've noticed some problems: the FM no longer works. It works randomly for a few seconds and the it stops; the AM tuner works very fine, same the cd player. Even I have no sound on the FM tuner, the FM scanning works and shows me the radio stations. I've noticed that at max. volume I hear some poor sounds as the aerial antenna it is not connected.
Any ideas? Could be from the immo of or a defective FM tuner?
Thanks!