Order by works either on strings, or numbers, but not both at once.
This is also visible in the native ordering of Posts in the Admin Posts list - WordPress orders natively by string and hence will break numerical ordering to a string ordering.
It does the same with special characters.
This means, a string will be ordered alphabetically, a number or special character will be interpreted as a string and hence be ordered by the number of characters in that string since one cannot order numerical values by string or opposite.
If set to ASC, such query first returns Special Signs from 1-N items (unless there are letters in the string of special characters, then it's first N of special characters, second the letter from A-Z), then Numbers from 0-N, then letters from A-Z or the other way around, first letters from Z-A, then Numbers from N-0, then Special Signs from N-1 item.
So your only chance to have those at the bottom is to change from ASC to DESC in the allover ordering.
On another hand, one would need to alter the query and loop in custom regex as shown in this Post to only order by Letter, let's say:
https://stackoverflow.com/questions/11641370/how-to-sort-mysql-results-with-letters-first-symbols-last
You could maybe simply exclude those posts from the results altogether.
There are several ways to do this, but the best would be to validate the input (In Forms, or wherever people create posts) ensure only expected data is submitted. This can be done with custom validation code or using specific fields, and more.
Another option is to validate the output before passing it to the queries with a filter of Views https://toolset.com/documentation/programmer-reference/views-filters/#wpv_filter_query
Please let me know if you need help with validation of input, I can give a few ideas on how to achieve this.
Mainly you'd hook on a cred_save_data() action and simply delete unwanted characters from the post, or, you could use Forms Conditions to not even let the user submit the Form if they use special characters.
https://toolset.com/documentation/programmer-reference/cred-api/#cred_save_data
https://toolset.com/documentation/user-guides/conditional-display-for-form-inputs/
