Thank you

@rvrv not entirely correct views\default\errors only get used for http exceptions

all other exceptions \ errors get handled by views\failsafe\excpetions\. admin_exceptions.php for site admins and exceptions.php for users.

If you enable the developers plugin (bundled with Elgg) the admin_exceptions get overruled with more information to help you debug, so no need for custom code (but you could)

Thank you @Jerome

However, I do not know how to use it. Could you please give me some guidance.

Thank you very much.

The user language selected in the user settings overrides the selected site language. Which language is selected in the user settings of the admin user? Maybe you've changed the language there without wanting to.

Yes, you are right. Admin user was changed somehow to Spanish. It is OK now.

Thank you very much

Than you Jerome but the problem is with a version for Elgg 2.3. Please see below.

I meant v3.x of the plugin ;)

I uploaded a new version where the zip should be as expected. https://elgg.org/plugins/1939122/releases/3.2.2

Still it's larger than the other versions, as explained above.

Thank you very much

1 - Every time after these changes you must clear the cache.

2 - Perhaps, some plugins have the same view.

3 - You can try to unextend this view in your custom plugin:

elgg_unextend_view('forms/attachments/upload', 'input/attachments');

4 - If you make this change in your custom plugin, make sure it's moved after the original plugin by priority.

Learn more methods.

Thank you RvR. 

I did all your suggestions but it still does not work.

Perhaps, some plugins have the same view.

I do not think there is other same view since when I comment the whole input/attachments.php its content disappears from the page (as desired).

The mystery is what causes this view to appear. 

Generally speaking I prefer replacing (not just overwriting) the vendor folder and the Elgg core bundled plugin folders in the mod directory plus checking for differences in the files elgg-config/settings.php and and .htaccess that might need to be resolved. In case of an update from 2.3.10 to 2.3.11 a comparison showed that there are no files in 2.3.10 that are no longer there in 2.3.11, only a few new files in 2.3.11 and then only changed files. So, when updating from 2.3.10 to 2.3.11 you could just overwrite the mod and vendor folders and overwrite composer.json and composer.lock files in the main folder and it should be alright. Nonetheless, a backup of the database should always be made first before upgrading (and making a backup of the install folder and data directory regularly is a good idea, too). After overwriting the files you would run upgrade.php (or clicking on the Upgrade button in the admin area) and you should be done.

http://learn.elgg.org/en/2.3/admin/upgrading.html

Very helpful.

Thank you very much