PHP Warning: unserialize() expects parameter 1 to be string, array given

I’m seeing errors like the ones below in my error_log file:
PHP Warning: unserialize() expects parameter 1 to be string, array given in wp-content/plugins/geodirectory/includes/custom-fields/output-functions.php on line 2290

This line specifically:
$extra_fields = stripslashes_deep(unserialize($cf['extra_fields']));

I am using a persistent Object Cache (the Docket Cache plugin) which unserialized the values stored in cache so your plugin is unserializing it the second time.

Maybe changing unserialize() to maybe_unserialize() will solve the problem?

Here’s a reference of the same problem happening to another plugin:
https://www.ads-software.com/support/topic/php-warning-unserialize-expects-parameter-1-to-be-string-array-given/