Wordpress site crashes on checking one options in theme setup

Job ID: 31526274

Budget: $30 – $250 USD

After checking the "iframe" option in the wordpress theme, the site crashes. The site is a news aggregator that opens external pages in an iframe browser. When the option is unchecked everything is fine. This problem happened after upgrading LAMP on server PHP was 5, now is 7.4
Related categories: PHP WordPress Apache MySQL HTML