Error: Maximum execution time of 30 seconds exceeded

On some pages I get 2 error messages "Error: Maximum execution time of 30 seconds exceeded" (see attached image).

Examples of test site: https://test.rivistasherwood.it/riviste/archivio-riviste.html
In addition, we noticed a general slowdown in loading the site pages.
Can you help us solve it?
Thanks.

PS: To see the button in all the articles of the website, we have inserted the code {msl_button aid="15" cp="wishlist"} in the override of the default.php page of the joomla articles. Is it ok or is there a better way?,
Thanks again

Hello there and thank you for posting!

This is caused by the System plugin. Please go tk
o System - MyShortlist button and in the advanced tab, disable the Use DomDocument option.

Some templates and websites are structured in a way that PHP's simple DOM analyzer can't handle.

Adding the button as you did is correct and will work well even after disabling this option.

Let me know if you need any further assistance. 

Perfect!
Now the pages open correctly.

A question about the button code inserted as indicated above:
I created a "My ShortList" module and in "Menu assignment" I indicated the menu items where it should appear.
However, the button appears in all articles, regardless of the menu items.
In those that I did not indicate, moreover, it appears in English (instead of in Italian as I translated them).
Is it possible to make the button appear only in the articles indicated in "Menu assignment"?
Thanks again

I'm glad we fixed the loading time issue.

Well, I understand what you mean, but since you load the button in the template override, MyShortlist tries to show it, regardless of whether a module exists to load options from.
If a module doesn't exist (in the menu items that you haven't selected) the default options are loaded, hence the English text.

I think the best way to go would be to check for the existence of the module in your template override. I'm not 100% sure if this could work, but perhaps you could use the countModules function from the template:
Let me know if that helps.

 

Thanks,
I'll try to work on it