Enclosing the shortcode fixes many problems

Shortcodes come in three flavors:

• self-closing: [strong]
• enclosing: [strong][/strong]
• self-enclosing: [strong ... /]

When using multiple [strong]‘s on a page and any of them wraps content or has child shortcodes, each one must be enclosed with [/strong]. This seems to work better than the self-enclosing [strong ... /].

If there is only one [strong] on the page, it would not require the extra closing [/strong].

When in doubt, go with enclosed. See Enclosing Shortcodes to learn more.

For example, this will not work because the first shortcode is not enclosed:

[strong form]
...
[strong per_page="3]
  [client]
    [field name="client_name" class="name"]
  [/client]
[/strong]

But this will:

[strong form][/strong]
...
[strong per_page="3]
  [client]
    [field name="client_name" class="name"]
  [/client]
[/strong]

When counting [strong]‘s, consider the entire page, not only the main content field. Include any that are embedded in page builder components, text widgets, or template files.

https://www.ads-software.com/plugins/strong-testimonials/