PHP error due to Ajax request & slow page load

Hello how ‘re you? The plugin is very useful (One of my best!), but I’m receiving a PHP error in pages that have it. I leave you a screen: https://prnt.sc/spboyg so you can check the messages from Query Monitor plugin & developer console.

Is a pricing page with only 5 tables, and between [calculate][/calculate] are prices shortcodes and discount shortcodes… Easy multiplications.

Also, It slows down the load time(No other shortcodes are working in the same pages, only #calculate).

Any ideas?
Thanks a lot!