I have a Sony Z7U as well as an FX-1000 for weddings. While shooting the reception, we sometimes have to get close to the band or DJ's speaker system. I know that the music is way to loud for the onboard mic to handle, so we started switching to manual and cranking it down a bit. I'm still getting the crackling sound, but I don't know how much more I can do.
I wanted to know if there were better mics that could handle this situation. I would also like to know if there is a good replacement for the onboard audio for each camera. I assume FX-1000 uses a basic Omni directional style microphone.

TIA

It must be very very loud as I have done discos with the Z7 on auto level in my pub and have had no problems with the levels at all and that is with a 600 watt system banging away.

You're slamming the inputs or overloading the cheap onboard mic on the camera. Does your camera have a microphone attenuation setting? Turn it on if you do. My suggestion is more physical than electronic. Don't stand in front of the speakers.

I have a Sony Z7U as well as an FX-1000 for weddings. While shooting the reception, we sometimes have to get close to the band or DJ's speaker system. I know that the music is way to loud for the onboard mic to handle, so we started switching to manual and cranking it down a bit. I'm still getting the crackling sound, but I don't know how much more I can do.
I wanted to know if there were better mics that could handle this situation. I would also like to know if there is a good replacement for the onboard audio for each camera. I assume FX-1000 uses a basic Omni directional style microphone.

TIA

As Brian said ... most likely you're overloading and clipping on the preamp input circuits. These are well before the recording level controls and turning those controls up or down just changes the volume of an already distorted audio signal.