Crackle from tweeters with bluetooth kit

Hey folks.

Hoping someone can shed some light on this.

I have an iO Play Bluetooth kit. It has it's own separate amp and just mutes the stereo when it kicks in.

I had it fitted to the Cordoba that had 4 speakers and 4 tweeters.

It was fine and audio quality was good for both calls and music streaming.

I have fitted it to the Octavia. It also has 4 speakers and 4 tweeters.

It works but when listening to music the tweeters crackle. It's not constant but quite noticeable.

What could be causing this? It's just the tweeters so surely can't be the amp/kit itself? Is it giving them too much power?

Many thanks for any help.

Phil