Debugging middleware in Express.js can be pretty tough. This is mainly because of how it handles things at the same time and the many ways it can work together. Here are some common problems you might face:

• Hidden Errors: Sometimes, middleware can fail without showing an error message, making it hard to find the problem.
• Execution Order: If the order of middleware is wrong, it can cause unexpected results.

Here are some solutions that might help:

1. Detailed Logging: Use logging to keep track of what the middleware is doing. This will help you see what happens step by step.
2. Using a Debugger: Try using tools like the Node.js debugger or Chrome DevTools to watch your code closely as it runs.

Even though it can be difficult, these tips can help you find and fix issues more easily.