I’m using the EZ Drummer basic kit percussion map created by the great Paul Walmsley. I’m getting good results in Dorico 5. Paul’s map is an ideal starting point if you wish to edit it for additional EZX drum kits. Perhaps comparing Paul’s map to yours will help you with your troubleshooting.
I created a quick test video here: quick EZ Drummer 3 test with Dorico 5 - YouTube