recursive_unserialize_replace(): The script tried to execute a method or access a property of an incomplete object.

[Chematronix]

I uninstalled a plugin (Duplicator) without configuring it to delete its settings. Turns out these include its own serialised object class, making S&R fail with:

PHP Notice: Inpsyde\SearchReplace\Database\Replace::recursive_unserialize_replace(): The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "DUP_Package" of the object you are trying to operate on was loaded before unserialize() gets called or provide an autoloader to load the class definition in /var/www/html/wp-content/plugins/search-and-replace/inc/Database/Replace.php on line 355

The offending value in wp_options looks like:

O:11:"DUP_Package":25:{s:7:"Created";s:19:"2019-11-29 19:55:03";s:7:"Version";s:6:"1.3.24";s:9:"VersionWP";s:5:"5.2.4"...

Deleting this option (and all others from Duplicator) allowed S&R to work, but here's a possible permanent fix: https://github.com/interconnectit/Search-Replace-DB/pull/251/files/cccedfd2d6cc26447edecf457c4339d6fd6b0bb0

(This seemed to be already taken care of at #93)