Refactor store for better readability

**Problem**
When working with controllers, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

No file, test, or controller entry point is named. Start by locating the controller code and reading its current error-handling paths; clarify which messages and failure cases should change before editing. Done means the agreed error handling is implemented with more descriptive messages and the relevant checks pass.

Written by the indexing model from the issue text.