The phrase "challenge occurs" is correct and usable in written English.
It can be used to describe a situation where a challenge takes place or arises.
Example: "When a challenge occurs, it is important to stay focused and find solutions."
Alternatives: "challenge arises" or "challenge presents itself".
"About the tackle: If the ball is overrun by the opponent and a 50/50 challenge occurs, collision is inevitable.
(The only real challenge occurs when moving Quico from platform to platform in some of the later stages, and it feels unintentionally exasperating).
One critical challenge occurs when part of a semiconductor fabricator׳s capacity is allocated to produce wafers designed by and provided to fabless companies.
Our leadership challenge occurs in three broad demographics: young, emerging leaders who are currently somewhere out there in our education system; developing leaders who are out in the world right now, engaged in doing work and navigating their own development and growth; and current leaders who are already in critical positions of influence.
Taking preventative action strengthens the weaknesses before the challenge occurs, so when up against a personal battle, a line of defense is already in place.
This challenge occurs in a setting that limits physiologic monitoring and visualization.
I resigned to make that challenge occur".
For Ms. Bakoulis, the first challenge occurred three months after their first child was born, in October 1997, when Mr. Ruben's mother (deceased 10 years now) flew out to visit.
The engineering design challenge occurred on the final day of the workshop after participants had been exposed to engineering and engineering design-based STEM experiences on the previous day.
That is how the current challenge occurred.
Blood was taken seven days later for measurement of immune responses and sporozoite challenge occurred 5 days after this blood sampling.
