Improve error messages in store

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

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

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

Start by locating the route-handling code and the store implementation, then trace where the current errors are created. Identify the cases that need more detail and confirm the expected wording with the maintainers; done means route failures produce descriptive messages and the relevant behavior is covered by tests.

Written by the indexing model from the issue text.