As I have not seen your plug my response can be at best somewhat speculative.
Ares has a limit on the number of objects a level can handle, also on the number of different sprites (=items, ships, weapons fire, asteroids planets, bugs etc). this only becomes a problem on heavy combat scenarios. In my plug Audemedon Crisis I pushed the "sprites" limit right to the edge. I wanted to create a big battle involving lots of races. I ran out of sprites. My final solution was to reduce the number of weapons sprites by creating Human Gunships which were armed with Ishman weapons, this knocked about six sprites off the sprite count for the level. Try creating a copy of your plug and delete an entire ship class (which will reduce the sprite count by maybe 10) to see if you get the warning. Continue deleting ship classes (ie all the HVDs of a particular race for example) until you no longer get the sprite warning). To continue using a ship class that had to be deleted to bring the sprite count down you will need to re-equip the ship class with weapons already used by other ships in the level (bearing in mind that each ship itself will occupy a sprite count of at least one). This is a bug that can be fixed, and this is how I fixed it when I encountered it. There may be other solutions also.
Remember also that Ares loads each sprite only once. So 50 HVDs of race X will load, maybe 20 sprites say (=ship+weapons+anything else generated by the ship). One HVD of race X will load the same number of sprites. you can use this to your advantage by re-arranging weapons allocated to ships, or weapons' fire sprites.
Again, this bug is totally fixable.
The sound bug is linked to that of weapons sprites, and will generally fix itself if you fix the sprites bug.
Adjusting the memory allocation to Hera and or Ares will not help.
Another word of caution, keep an eye on the number of objects that are created in your plug. Ares will allow approximately 1200 in a plug. Above that and my experience is that the plug is corrupted irrevocably.
Additionally, in this age of gigabytes of Ram and (almost) terabytes of hard disk capacity make back-ups of your Ares scenario. I back up my file each time I make any change on it. This is useful in troubleshooting bugs as well, as it enables you to trace back the originating point of a bug. You would also be well advised to keep a back up of Ares and of Hera, and of your Ares Preferences file, just in case.
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Oh, so it is another bug hunt then...
Just wait and see...