Backpack Can't Be Loaded When Sprite Was Either Deleted Or Added

[q019278]

Greetings, I have a bug when I was doing another project but I want to delete something from the backpack but when I delete or add a costume or sprite, it shows the error: "Error loading backpack".

Expected Behavior

Normally backpack in Scratch are used to store many sprites and costumes including codes. Sprites and others can be added or deleted when hover onto the backpack.

Actual Behavior

The error message appears as the backpack left unchanged when reloading.

Steps to Reproduce

In order to check to see if you have one, follow these steps:

1. Go to 'https://scratch.mit.edu/...'
2. Click one of your projects.
3. Once the project is loaded, click "See Inside".
4. Then click on the backpack.
5. If the backpack was fine, then it should have no problem. If not, download the costume but not code or one whole sprite.

System Details

If the problem occurs in the browser, please provide operating system and browser e.g. Mac OS 10.11.6 Safari 10.0

If using one of the Apps please provide the app version and device details, e.g. Scratch 3.0.57, Android 9 on HP x360 Chromebook

Screenshots

This shows the error when added or removed a sprite. When reloading, the backpack was unchanged.

Conclusion
I hope this error/bug will be fixed anytime soon so it will be suitable for all Scratch users including me.