I noted that the field names alphabetize differently it the measure and dimension lists, than they do in the filter list. See the attached example. In the measure and dimension list at the left, alphabetization is case-insensitive. In the filter pop-up upper case seems to have priority (see MO Claim and LT Claim in the list).
Thank you for making us aware of this! I will log it so that it can be fixed in an upcoming release!