I used to have the occasional crackling issue with music but a factory reset of the head unit seemed to resolve this.
However I still get the phone call echo issue. It's irregular but when it happens the person I'm speaking to says it sounds like I'm underwater. I've done a test when this last happened and pulled the lead out so the phone went into bluetooth calling and this fixed the problem on the call. I've not tested it again.
The CPlay2Air is a good shout and I think in theory would resolve the issue. I recently got a similar unit from Transporter HQ. Mainly as I didn't want to always plug the phone in (I've got a T6.1) to have music. I've had it a few weeks and not had any issues with phone calls, I've only had a few calls. Seems a good unit, it takes 30sec-1min to load through a few screens before you're into the Carplay menu which you get used to quickly.
Here's a link to the Transporter HQ device
Totally wireless connection that is plug and play. Available for vehicles with original car play system and controlled by OEM touch function or buttons. Supports high resolution with no need to install as it connects via USB port.
transporterhq.co.uk