Fix Data Bugs in ASP.NET

Several functional bugs are stopping my ASP.NET application from handling data correctly. The problems sit squarely in the data-processing and storage layer: records occasionally fail to save, some queries return inconsistent results, and a couple of stored procedures time out under load.

Source code is in C# with Entity Framework talking to a SQL Server back-end, and all changes are tracked in Git. I can provide a concise bug list, steps to reproduce each issue, database scripts, and remote access to a staging environment.

Deliverables
• Clean, well-commented code patch (pull-request format) that fixes every listed bug
• Confirmation that unit tests and regression tests pass
• A brief changelog explaining what was fixed and why

Acceptance criteria
All data operations—insert, update, delete, complex query—must execute without errors and persist the correct results across page refreshes and API calls. No new warnings should appear in the Visual Studio build, and performance must remain at or above the current baseline.