Unload files(rpg maker mv)

When I create a game the software doesn't load lots of files (Audio and animations). Sometimes even if I put them the software seems to not recognize them. It happens when I choose the option where I create a game with only the used file and not all of them. The problem appears only in battles, and usually with the same files. The only plugin I use for battles is the battle core engine

If the software does not recognize them, then most likely your filenames does not conform to networking rules.
Windows allows you to use filenames that break the network rules, but because MV needs to be able to deploy to different devices and operating systems it requires files that follow those rules - besically no spaces, only latin letters and only a limited number of special signs.
If your filenames contain even one of the forbidden letters, the engine will not be able to use them until you rename them correctly.

The files' names are Hit1.png and Howl.png and they don't break any rules, it is so strange because it loads hit2 hit3 but not hit1

@Koblas and there you hit yourself on the one rule about networking filenames that I forgot to mention.
Why should the engine load the file Hit1.png when it requires the file hit1.png?

Under networking rules, Hit1 and hit1 are two different files, because H is a different letter from h (capitalization counts on networks).
Only Windows has an override that redirects to the wrong file, no other operating system is that stupid.

However, it could very well be something else that caused problems for you here - you don't give enough information to identify where your error could be coming from.
For starters, please tell us the full filepath to your project (drive letter to index.html), tell us which version number your projects rpg_core.js file has (open with a text editor and check the title line) and post a screenshot of your plugin manager.