HELP! WordPress keeps crashing when I try to edit my header.

Hi there,

I'm hoping someone can point me in the right direction on how to resolve this.

I'm using Botiga and wanted to try BreakDance as I've read that is is very light.

I noticed that my logo was missing from my header and went to edit my header via Botiga but it crashed my site and I get the 'There has been a critical error on this website. Please check your site admin email inbox for instructions.'

I then created a staging site, uninstalled Botiga and installed BreakDance, and I get this error when I try and add a menu 'An error occurred while running an inline script from "onMountedElement" for element with ID "123". Error:"TypeError: Cannot read properties of null (reading 'addEventListener')"

I also get the critical error message when I go on 'Appearance' - 'Customise' or 'Header'

I'm assuming that the problem is related to Java Script, I've Googled it and getting loads of results mainly for non WordPress sites but I'm totally confused as to which part I should be editing and what needs altering.

Any ideas please?

Thanks