The phrase "are substantial issues" is correct and usable in written English.
It can be used when discussing significant problems or concerns in a particular context.
Example: "In our recent meeting, we identified that there are substantial issues regarding the project's timeline and budget."
Alternatives: "are significant concerns" or "are major problems."
Calls for groundwater resources management and international attention to groundwater are substantial issues since the process of developing and managing this vital resource in a sustainable mode discomposes many challenges (Zuppi 2008).
41 There are substantial issues regarding a profound lack of understanding of the death and dying experiences of older individuals.
There are substantial issues raised with the immunity angle that need to be addressed through further experimentation for the paper to be acceptable for eLife.
For each of the five properties, a judgment is made and documented regarding whether there are substantial issues that decrease the confidence rating in each aspect of the body of evidence for the outcome.
Visual screening appears to be a simple, safe, acceptable and inexpensive approach but there are substantial issues related to test accuracy and repeatability of visual screening, and screening with visual inspection was not found to decrease cervical cancer mortality in a large-scale trial in rural India [ 19].
As we have seen, there are substantial issues of liberty which would also need to be resolved and which could conceivably be threatened by any measures that make the freedom to do immoral things impossible, rather than simply making the doing of them wrong and giving us moral, legal and prudential reasons to refrain.
Trump almost has a point: There were substantial issues with pre-election polls.
Outside experts hailed the new research as promising, but cautioned there were substantial issues of safety and effectiveness to be worked out before it could be ready for widespread use.
There are substantial metaphysical issues about the nature of facts, objects, and properties, and the relationships between them (see Mellor and Oliver 1997 and Lowe 2002, part IV), but these are not of concern here.
Yes, I know that there are substantial legal issues in bringing the facts before the public.
These physicians acknowledged that there are substantial systematic issues, but they should also reflect on whether physicians have been serving the best interests of patients.
