I know this is a very known problem in SC2 editor. When you duplicate a unit, you have to link the actors and sounds too.
I didn't duplicate any unit nor changed its name either. I just changed the damage amount some weapons do and when I test my map most of the ground units (Like Hydralisks, Marauders, Marines...) don't show the attack and attacking sounds.
The actors and sounds are linked to the units properly. I didn't touch anything else but the damage amount of the weapons.
When you change any properties of the unit, lets say the life amount or the armor, the SC2 Galaxy Editor makes a copy of the unit automatically. The copy of the unit has the same name of the parent unit, but it doesn't have the actors and sounds linked.
This is very annoying, I Hope Blizzard will correct this problem soon.
It does copy automatically sort of. It keeps a backup of the original, un-edited version in blue text, and your version in green text. You can not touch the original backups, or use them in the map. Its like they don't exist. They're just there so you can hit "revert to parent settings"
Rollback Post to RevisionRollBack
Feel free to Send me a PM if you have any questions/concerns!