This issue was resolved in the May 2018 release of Connect RE. Connect RE has an auto-update feature which will automatically upgrade your version when users launch the application from Raiser's Edge.
NOTE: When a profile in Core has a gender value of "Other", the matching record in Raiser's Edge will have the gender value of "Unknown."
This means the gender values in Core and Raiser's Edge may not be identical if the "Other" value is selected in Core, even after the data syncs. However, the sync does not result in a blank or binary-gendered value for Raiser's Edge records either.