I'm on Opencart 1.5.6.1 and VPS server. I do not often change the images of my products, but in this case I see a concern. When I want to change the image of a product, after validation, I have the admin login page that appears in place of it. If I go out of the page and I come back, my image has been validated and is in its place.

More images in the manager are not visible when in the front everything is OK:


This code is inserted instead:

Possible related /admin/view/template/common/filemanager.tpl file as seen on anglo saxon forums, but I can not find the solution, let alone how does it came to be.
Any idea?
Thanks