Can't edit my module, blank page with an select input

Question

This is probably a difficult question to ask because I can't give a lot of information. When I open the edit screen in the admin-side of a module, it's being shown for a split second and then the page refreshes to a blank page with a select field.

I already tried to uninstall the admin template and reinstall, but the issue is still here. It happens with any admin template that I tried so far except the oldschool Hathor admin template.

I have no idea where to look for the problem. I hope someone else encountered this issue before and has a solution ... or at least has an idea where to look.

Tell me if there is any information I can give to help clearify my question.

p.s. I am running the latest Joomla version (3.6.5).

My screenshot:

Answer 1

I Fixed it by reinstalling Joomla core files.

First make a back-up. Then components -> Joomla -> install

ps. this is available form Joomla 3.6.x

Answer 2

This issue does not require to re-install Joomla. All it takes to fix this issue is make sure to clear Joomla's cache and browser cache and refresh the page.

It's a caching issue usually after updates, as some js have been changed for the backend, but the backend still loads old cached js.