I downloaded and checked your project Proyecto 2_Mar22-2026_9-30-44.zip (62 MB).
This project includes one heavy custom transition (10 variants, 62 MB, 20 video files). It's included as Embedded transition (local project storage). It means that it's included in the project (not in the global storage). For this reason, the program doesn't clean up its resources, even if no slide uses it. This is because the transition is stored in a single, unique instance - in the project's resources.
If the transition is in the program's global storage, the program (PTE AV Studio) automatically cleans up the project's resources as soon as all slides stop using it (when the project or PTE AV Studio is closed).
To resolve this particular case, simply remove the transition in the list of transitions in Project Options / Slide Options and close the project.
Be careful - re-check that you have a copy of this transition before deleting it.
If you didn't specifically create this transition in the project's local project storage, this situation could have occurred for the following reason:
1. You created or imported a new transition into the program's global storage.
2. You used this transition in a project.
3. Then you shared a ZIP copy of the project with another user (or moved the project to a second PC).
4. PTE AV Studio always saves a local copy of the transition in the project, so you can correctly open this project on another computer where the transition isn't yet in the global storage and it won't be automatically added there.
5. Thus, the transition becomes a local transition (embedded transition). If you now stop using this transition, resource cleanup will not occur automatically.