Error after overriding a symfony controller

[Vignesh R]

we are having major problems in. the admin ... blank. white pages unable to open reductions or commandes unles in debug mode and. getting. a. blank screen with content coding error.

this is what I got from mode debug;

CRITICAL 08:00:51phpUncaught Exception: You have requested a non-existent service "mbo.tab.collection.provider".

CRITICAL 08:00:52requestUncaught PHP Exception Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: "You have requested a non-existent service "mbo.tab.collection.provider"." at /home/arigomot/www/var/cache/dev/classes.php line 3418

ServiceNotFoundException

Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: You have requested a non-existent service "mbo.tab.collection.provider". at var/cache/dev/classes.php:3418 at Symfony\Component\DependencyInjection\Container->get('mbo.tab.collection.provider') (modules/ps_mbo/ps_mbo.php:409) at ps_mbo->get('mbo.tab.collection.provider') (modules/ps_mbo/ps_mbo.php:388) at ps_mbo->shouldAttachRecommendedModulesButton() (modules/ps_mbo/ps_mbo.php:306) at ps_mbo->hookActionAdminControllerSetMedia(array('cookie' => object(Cookie), 'cart' => object(Cart), 'altern' => 7)) (classes/Hook.php:970) at HookCore::coreCallHook(object(ps_mbo), 'hookactionAdminControllerSetMedia', array('cookie' => object(Cookie), 'cart' => object(Cart), 'altern' => 7)) (classes/Hook.php:355) at HookCore::callHookOn(object(ps_mbo), 'actionAdminControllerSetMedia', array('cookie' => object(Cookie), 'cart' => object(Cart), 'altern' => 7)) (classes/Hook.php:907) at HookCore::exec('actionAdminControllerSetMedia') (classes/controller/AdminController.php:2745) at AdminControllerCore->setMedia(false) (controllers/admin/AdminOrdersController.php:340) at AdminOrdersControllerCore->setMedia() (classes/controller/Controller.php:277) at ControllerCore->run() (classes/Dispatcher.php:515) at DispatcherCore->dispatch() (admin421wxxufz/index.php:97)

it says. also http internal server error 500? flushed cache everything but this error seems to be recurring issue for me. We recently worked  on core file to override and remap the route using composer.json but after the major overall we are left with this backend error. please give me clarifications on how to resolve this issue