I need to map an area that crosses 2 UTM zones with ArcGIS for Desktop. After having defined the Data Frame projection according one of the two UTM zones involved, I have noticed that the MGRS labels are wrong for the part of the map covered by the other UTM zone. For example, in this map of central Haiti crossing UTM Zones 18 and 19 I have applied the projection UTM Zone 18N. As you can see, MGRS label are correct for all the 18Q grids, and wrong for the remaining 19Q ones.
Correct MGRS coordinates can be easily checked here: https://mappingsupport.com/p/gmap4.php?tilt=off&mgrs=14SPG34308382&z=5&t=t1
Is it possible to fix this issue, or at least to find a good workaround?