When you reverse the arity of an association with the “reverse direction” feature, this is not preserved in an XMI export.
Reproduce :
Draw a class diagram with two classes associated.
Reverse the arity of the association
Export to XMI
Reimport from XMI
Arity has reverted to original direction
Suggestions :
Export reversal flag as an extension property
Implement reversal operation as an actual amendment of the ends of the association instead of a boolean flag
About your step “Reverse the arity of the association”, may I know how you change this? By right click on the association and select Change From/To Shape?
This leads to the reversal of the solid black arrow (as shown from Customer to Reservation in the help) ; this appears to be stored as a boolean flag in the model which is not preserved on export to XMI.