ORCID iD's that end with an X are valid and correct.
The last character of an ORCID identifier is a Checksum. It ranges in values from “0” - “10,” with X representing the value “10.” The Checksum ensures the other 15 digits of your identifier form a coherent iD.
Please also note that if you are manually filling in your ORCID identifier that the "X" must be capitalized for the identifier to be valid.
You can learn more about the structure of an ORCID identifier here.
Identifiers are randomly assigned, and cannot be changed.