'functional problems' is correct and can be used in written English.
You can use it to refer to any difficulty or concern when it comes to a system working properly. For example: The computer has been having some functional problems lately, so we need to get it checked out.
Dementia is a state of cognitive decline sufficient to cause functional problems; thus, describing function is a critical component.
Such functional problems don't make Le Corbusier's immaculate geometries any the less thrilling.
Orthotics change foot mechanics by correcting functional problems or redistributing body weight.
Not treating these intangible, yet equally real injuries, may lead to long-term functional problems.
But the fact is that the vast majority of gastrointestinal complaints (like irritable-bowel syndrome) are functional problems that modern medicine cannot cure.
Such cultural and functional problems of definition seldom arise in East Asian music, and a more neutral definition is appropriate.
As in most other arts, garden and landscape design must solve not only aesthetic but also technical and functional problems.
The researchers found that the higher the score at the start of the study, the greater the likelihood that the volunteers would develop cognitive and functional problems over the course of the study.
"I would generally advise against this type of surgery unless the patient has functional problems such as pain or discomfort when exercising or during intercourse.
"There were organisational and functional problems with the house," says Jones. "But the major architectural issue was the way the building related to the topography.
Further extensions concern problems in abstract spaces, functional problems, multivalued problems, etc.
