Mk3 speakers reverberate when cold or damp

Hi all.

My 2006 NC Sport Soft top is very dry internally but since I bought it last year the Bose stereo is very reverby if it’s either damp or cold out. Often later the same day after driving it they’ll go back to normal. It seems to be some speakers sometimes and others other times. I sometimes fix it by adjusting all the output to go through the one that might not reverberate at that moment. It wasn’t so bad over the summer but had started playing up again as the weather has taken a turn.

Just wondering what if this is a common problem with a common solution. Not sure if it’s the head unit or the speakers or the connections or seals…

Thanks in advance.