"reason behind the problem" is correct and usable in written English.
You can use this phrase when you want to explain what is causing an issue or difficulty. For example, "The reason behind the problem is that the infrastructure needed to support this new system is not currently in place."
"I wanted him to reconsider his lifestyle, to not view his skin colour as the reason behind the problems he had".
I think there are many other reasons behind the problem".
The reason behind this problem is that local search methods tend to fall into local minima.
The main reason behind this problem might be a failure of the evaluation system.
Second, with the understanding of institutional logics in China based on the study, one may better explain the reasons behind the problems in the development of Chinese innovation systems.
A closer inspection shows that the discontinuity occurring on the boundaries' temperatures at t = 0, when a "ramp-type" of boundary condition is used, is the reason behind the occurring problem and the apparent paradox.
"This is the big, big reason behind all the problems we are talking about".
However, there is a lack of general guidance for researchers and healthcare professionals to choose the appropriate tools that can explore the extent of medication adherence and the reasons behind this problem in order to orchestrate subsequent interventions.
The product shortage — and limited information provided by the company about the reasons behind the supply problem — caused even louder howls of frustration among some women than the children's medicine recall.
To unveil the reason behind the moist-related problems observed, several samples of repair plasters and renders, as well as of the underlying historic masonry materials, were collected from representative affected areas of the building.
