Var_export warning filling up logs


My problem is more of a nuisance, but still I’d like your help. After upgrading a project from CakePHP 1 to CakePHP 3 I get these errors in my log:

2019-12-23 19:30:03 Warning: Warning (2): var_export does not handle circular re
ferences in [/[...]/vendor/cakephp/cakephp/src/Core/ObjectRegistry.php, line 147]
Request URL: /cronjobs/mail
Client IP: x.x.x.x
Trace: Cake\Error\BaseErrorHandler::handleError() - CORE/src/Error/BaseErrorHandler.php, line 159
var_export - [internal], line ??
Cake\Core\ObjectRegistry::_checkDuplicate() - CORE/src/Core/ObjectRegistry.php, line 147
Cake\Core\ObjectRegistry::load() - CORE/src/Core/ObjectRegistry.php, line 86
Cake\Controller\Controller::loadComponent() - CORE/src/Controller/Controller.php, line 335
App\Controller\ErrorController::initialize() - APP/Controller/ErrorController.php, line 39
Cake\Controller\Controller::__construct() - CORE/src/Controller/Controller.php, line 273
Cake\Error\ExceptionRenderer::_getController() - CORE/src/Error/ExceptionRenderer.php, line 166
Cake\Error\ExceptionRenderer::__construct() - CORE/src/Error/ExceptionRenderer.php, line 102
Cake\Error\Middleware\ErrorHandlerMiddleware::getRenderer() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 173
Cake\Error\Middleware\ErrorHandlerMiddleware::handleException() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 114
Cake\Error\Middleware\ErrorHandlerMiddleware::__invoke() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 100
Cake\Http\Runner::__invoke() - CORE/src/Http/Runner.php, line 65
Cake\Http\Runner::run() - CORE/src/Http/Runner.php, line 51
Cake\Http\Server::run() - CORE/src/Http/Server.php, line 98
[main] - ROOT/public_html/index.php, line 42

Otherwise the software runs fine; the errors are also present in my development environment. The main problem is that it happens multiple times for every call so the logs fill up fast, and it’s hard to find the real errors in between.

The one architectural change that may be related to this is that I use a plugin that acts as the base for the application. Here’s why: there are two websites with a lot of similar code. So the plugin contains all the common code, including Tables, Entities, Controllers, a Component and even some Elements. All controllers in the ‘real’ application are derived from a base controller in the plugin. Perhaps a bit weird, but I don’t see another way of doing it. Anyway, I’d like some pointers on how to tackle this problem. So far I’ve had little success in finding the circular reference, so any help would appreciated.