"problem in understanding" is a correct and usable phrase in written English.
You could use it to describe a difficulty that someone is having comprehending a subject or concept. For example, "We encountered a problem in understanding the new regulations."
Dr. Holden said one problem in understanding spanking's effects was that researchers were only beginning to study the practice in any depth.
The question is: why? "A major problem in understanding what happened when modern humans appeared in Europe has concerned the dates for our arrival," said Professor Chris Stringer, of the Natural History Museum, London.
In a liquid mixture, the vapour pressure depends not only on the temperature but also on the composition, and the key problem in understanding the properties of solutions lies in determining this composition dependence.
This student might have a problem in understanding the distributive property of exponents.
Revealing protein-DNA interactions is a key problem in understanding transcriptional regulation at mechanistic level.
The basic problem in understanding Philolaus' philosophy is thus to determine what he means by limiters and unlimiteds.
Problems in understanding the process of reimbursement lead to strained relations: "They do not understand the modality of reimbursement, so when we ask them to pay for medication we have to negotiate with them".
Computer modeling has yet to resolve some major problems in understanding the nature of intelligence, however.
There are two big problems in understanding whether an intervention works, whether it's a medical treatment or social intervention such as changing methods for teaching reading or testing approaches to crime and punishment.
A further source of bias could be problems in understanding the difference between analgetic drugs and prescription medication in the students.
One of the main problems in understanding the high latitude magnetosphere and substorm dynamics is the high-level turbulence that is constantly observed within the plasma sheet.
