To confirm, try switching to the unedited default Theme (Twenty Seventeen, etc.) for a moment via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), navigate to /wp-content/themes/ and switch to the default theme by renaming your current theme’s folder by adding "-old" to the end of the folder name. Alternately, you can remove other themes except the default theme (Twenty Seventeen, etc.). That will force your site to use it.

If you can install plugins, install Health Check. On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you, while you’re still logged in, without affecting normal visitors to your site.

https://theeventscalendar.com/function/tribe_get_custom_fields/

A likely spot to look for this in a custom Events template file, usually in a child theme.

$room_number = tribe_get_custom_field('Room Number'); // Old way, now broken
$room_number = tribe_get_custom_fields()['Room Number']; // new way, works