Please try to follow the steps listed below to update the theme and you will find our the culprit as well.
If you want to update the theme on your current site, then follow the steps listed below:
1. Take the complete backup of your site before updating the Theme for avoiding any inconvenience.
2. Deactivate all the third-party plugins before updating the Theme.
3. Take a Backup of your Custom Code and remove it from the site before an update of the Theme.
4. If you are using a Child Theme then Activate the Parent-Theme before updating the Theme.
5. Remove all the cache from your server, site and finally check back your site after removing the browser cache and check deeply what are the changes that occur on your site after that…
6. After that go to Appearance >> Themes and update the Theme One-Click automatically from there.
7. After that go to Appearance >> Install Plugins and update the Theme required/recommended plugins from there one by one.
8. After that check back your site after removing the browser cache and check deeply what changes occur on your site after that and if all goes well then.
9. You have to again Activate the Child Theme.
10. Again activate all the third-party plugins one by one.
Hope this will help you in resolving your issue.