Hi Alekos,
Thank you, I was able to log-in and do some tests.
I believe there is something affecting the built in get_terms() function. I have tested the order which the search requests the categories, which is the correct order:
[html]69, 3, 2, 42, 43, 49, 44, 45, 46, 47, 40, 38, 39, 70, 37, 63, 64, 51, 67[/html]
..but the functions returns them in this order (this is what is then outputted):
[html]2, 3, 40, 39, 38, 37, 42, 43, 44, 45, 46, 47, 49, 51, 69, 70, 63, 64, 67[/html]
This should not be happening, and I have no idea why that function returns the incorrect order, and it would be probably a nightmare to debug it.
Instead, I have quickly made a custom filter function, that replaces the current method of getting the terms bulk, at once, by getting them one-by-one, and then merging them to an array. Add this custom code to the functions.php in your theme/child theme directory (copy from line 3 only!). Before editing, please make sure to have a full site back-up just in case!
This should hopefully fix the problem.