Accented characters require 8 bits. Setting the following environment variable will correct the problem:
NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1
This environment variable can be set in the "appx.env" file or it can be set outside of APPX if desired. But, it must be set for an APPX session to properly store and retrieve 8-bit characters in Oracle.
If the environment variable is not set for APPX sessions that are initiated by the appxd connection manager, you will need to set it in the start-appxd.sh script or in the "appx.env" file so that all APPX sessions will run with the environment variable set.