The phrase "a challenging issue that" is correct and usable in written English.
You can use it when discussing a difficult problem or topic that requires attention or consideration.
Example: "The report highlights a challenging issue that needs to be addressed in our upcoming meeting."
Alternatives: "a difficult matter that" or "a complex problem that".
Clustering is a challenging issue that is heavily shaped by data used and problems considered.
However, designing optimal kernels is still a challenging issue that needs to be further investigated.
This is a challenging issue that needs to be solved for the magnetometry-based navigation system presented here.
From the Open IE works, we realize that the extraction of relations from text is a challenging issue that is still far from being completely addressed.
Security in the grid environment is a challenging issue that can be characterized as a complex system involving many subtleties that may lead designers into error.
A challenging issue that hinders the skin regeneration is the lack of blood vessel formation, which makes it difficult to develop bioprinted constructs that can biologically fulfill the requirements for skin regeneration (Xiong et al. 2017).
How to design practical algorithms to exploit SDR and MIMO capabilities to improve performance in multi-hop multi-channel MIMO-enabled SDR-based WMNs is still an challenging issue that needs systematic investigation.
"It's a dynamic, challenging issue that affects a great deal of America.
Climate change is a civilization challenging issue that requires a global consensus and legal obligation to act.
Within this framework, action analysis is a highly challenging issue that involves both computer vision and machine learning methodologies.
Climate change is a civilization challenging issue that mandates active U.S. engagement with our entire global community.
