Radio volume spikes when listening to 106FM

Trojan

Looking for some help or advice with what's becoming a stranger and stranger audio problem. The issue is the radio volume is spiking up to very loud at times.

Example linked below. Be warned, the audio spikes loud in spots, I've reduced the gain on this clip but check you don't have speakers up loud before playing.

https://soundcloud.com/alastairmcdermott/bmw-business-radio-audio-volume-spikes

This is the BMW Business Radio in my 2002 E39 525i. The radio volume spikes at times as can be heard in this clip. This is a particularly bad instance of it happening - normally it happens less frequently (once every 10-20 mins). I was doing some testing and subjected myself to the horror of listening to 2FM for 15 minutes - no volume spikes. So it's only happening on Newstalk106 so far. Haven't tested on other frequencies yet

There is a Dension bluetooth unit installed (the blue Gateway Lite BT) in the glovebox wired in by a previous owner. The FM radio channel audio spike can be heard when the radio is in both normal radio mode and in CD mode (while playing bluetooth audio it cuts in about 0.5s of very loud audio from the radio channel).

Anyone know what the problem might be? I was wondering about loose wires and checked the Dension unit - snug fit for input cable. The other thing that could be related or just coincidental is weather - it was really bad when heavily overcast with solid rain when I recorded the above, this is significantly more frequent than normal.

Any ICE or physics experts who can explain what's going on here?

Trojan

Ok, this is strange. I was doing some testing and subjected myself to the horror of listening to 2FM for 15 minutes - no volume spikes. So it's only happening on Newstalk106 so far. Haven't tested on other frequencies yet. Anyone? Any physics experts who can explain what's going on here?