"difficult to debug" is correct and usable in written English.
You can use it when referring to a computer program or piece of code that requires a lot of work and effort to troubleshoot and resolve any errors or issues. For example, "This computer program is quite complex and is proving to be very difficult to debug."
After initial testing we found that Schematron scaled poorly with the complexity of the rules and was difficult to debug.
Leveraging skills and device driver code from one style of behavior to another leads to firmware defects, some of which are very difficult to debug.
Gmail is difficult to debug on the client-side because Gmail is written using the Google Web Toolkit, which outputs Javascript and CSS that isn't really intended for human consumption (have a look at the CSS class names, or just the source to the main page itself as examples).
It is difficult to debug workflows in the cloud without heavy logging.
Some error are very much difficult to debug while other are comparatively easy.
It is hard to debug JavaScript errors after the code is minified.
Instead of one huge, complex, difficult-to-debug-and-maintain piece of code, the software is broken into much more manageable independent functions on different central processing units (CPUs).
"From a developer standpoint, one added constraint with augmented reality is because it depends on the real world it's difficult to debug… so we've developed tools so that you can play back logs.
Excessive use is made of mutable singletons which, while aiding performance by eliminating the need for re-initialisation of components, allows for complex interactions in the code, making it difficult to understand, debug and re-factor.
While these scripts had full access to Cytoscape's comprehensive public API, their tight coupling to the Cytoscape runtime made them difficult to write, debug, and maintain.
Wireless sensor networks are notoriously difficult to program and debug.
