Mobile menu not working

Hi all,

The mobile menu on my page is not working: the hamburger is clickable, but will not expand. Upon reading the possible solutions on this forum, I disabled all plugins, this did not help. However, using the parent theme did make the menu work again (I also checked for javascript errors, but there were no additional errors between the parent and child theme).
I made several changes in the code of the child theme, also to header.php, which I thought contained the relevant code. However, restoring the parent theme header.php did not solve the issue. Therefore, could you perhaps point me towards the other files that are involved in showing the mobile menu so I can check the changes I made to these files in order to resolve the issue?

Thanks in advance,
Best, Ben

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