All ku faced a very strange problem, which is also playable only in a limited range of applications.
There is Elementor pro, it's a wonderful opportunity as the creation of templates. That is, it is a page Builder but with the ability to then embed it using shortcode.
So the problem is this: when working with the usual pages all is OK, but as soon as I try to save the template I get the error from admin-ajax.php
HEX color () needs to be 6 or 3 digits long
All happy, and I would appreciate any leads.