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A feature broke right after a plugin update

The site stays reachable, but one specific feature stopped working right after a plugin or theme update: a button that no longer responds, a block that vanishes, a checkout step that gets stuck. That’s a different case from a critical error that takes the whole site down: here, two plugins that used to coexist fine suddenly step on each other’s toes.

Describe my issue Send a message

How I go about it

  1. Enabling the error log

    I set WP_DEBUG_LOG to true in wp-config.php so any PHP error tied to the broken action gets written to wp-content/debug.log.

  2. Reproducing the exact action

    I reproduce the exact click, display or step reported, to see whether the error is constant or depends on a specific context (user role, device, cart contents).

  3. Reading the right kind of error

    An error in the browser console points to a JavaScript conflict, handled differently from a fatal PHP error in debug.log: the two need a different read.

  4. Isolating by targeted deactivation

    I deactivate suspect plugins one at a time, or use a plugin like Health Check & Troubleshooting to test under clean conditions without affecting visitors on the live site.

  5. Deciding on the fix

    Once the faulty pair is identified, I fix the conflicting hook priority, or assess whether one of the two plugins needs replacing.

What I handle regularly

  • A button that worked fine no longer responds after a plugin update
  • A Gutenberg block or a shortcode suddenly disappears from the display
  • One specific checkout step gets stuck, while the rest of the site works normally
  • The site stays perfectly reachable everywhere else, no critical error message
  • The browser console shows an unfamiliar JavaScript error, with nothing in the server logs

The real causes of a plugin conflict

Three mechanisms come up most often. Two plugins hook the same action or filter with priorities that clash, and the execution order shifts after an update. A JavaScript conflict happens when two plugins each enqueue a different version of jQuery, or the same script twice, silently breaking a click behaviour. Finally, a "cannot redeclare function" PHP error can appear, limited to one specific code path, without ever touching the rest of the site.

The distinction between a JavaScript error and a fatal PHP error isn’t a detail: a browser console error leaves no trace in debug.log, and vice versa. Plenty of merchants look in the wrong place before diagnosis even starts.

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Frequently asked questions

The site stays online, is it really serious?
It depends on the feature affected. A broken display block can wait; a stuck checkout step costs sales every minute, even while the rest of the site runs normally.
How do I know which plugin is at fault?
By deactivating plugins one at a time until the symptom disappears, or by isolating the exact error in debug.log or the browser console, which often points straight at the faulty file.
What is the Health Check & Troubleshooting plugin?
An official WordPress plugin that enables a clean troubleshooting mode reserved for the logged-in administrator: I can deactivate plugins to test without visitors seeing anything different.
Should I switch plugins if the conflict comes back every update?
If the same conflict reappears with every update, patching it repeatedly costs more over time than replacing the less essential plugin with a compatible alternative.
How long does it take to isolate this kind of conflict?
Once access to logs and the admin is available, isolating the faulty pair of plugins usually takes a few hours. The fix itself depends on what’s actually conflicting.

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