Given, your error occurs because you need to update the platform first and then plugins.
First of all, don't forget to Back up your website. If you faced the issues during the update process then just restore your site and perform the update in the following order:

1. deactivate all third-party plugins.
2. turn on 'Maintenance mode" in Admin Panel >Pages&Menus > Maintenance Page
3. enable DEBUG mode ( set to "true" in ow_includes/config.php)
4. perform platform update.
5. update all native Oxwall plugins. Don't check your site until you update all of them
6. update your theme.
7. enable DEV mod in ow_includes/config.php
8. Turn "Maintenance Mode" off.
9. refresh any site page and disable DEV MODE: define('OW_DEV_MODE', false);

We've tested update and if you do it in a right way, you won't face issues.

Given, have you managed to fix your issue?
If it's still exist, please open /ow_updates/classes/updater.php file and check whether you can find  getMobilWidgeteService() code. If you find it, you will need to replace it with getMobileWidgeteService() code. Then go to Admin panel, use my instructions on how to perform update correct and launch the update process again.