To correct this issue. we have created a hotfix. This is included in the APM10.5.1HF36_DE312165. To get access to the file, open a Support case at http://support.ca.com and request this hotfix.
As a temporary work around until you get this Hotfix, reset the APM Database password, then test and save. Once you have the correct password saved, then you can make a copy of the tess-db-cfg.xml in the <EM Home>/config folder. If needing to restart the MOM again, replace the tess-db-cfg.xml with your working saved copy to get everything back to normal.