[rear|raise] its (ugly|) head

(of a problem or unpleasant situation) to appear or become noticeable often unexpectedly

The idiom "rear its head" is associated with problems, issues, or negative situations reemerging or becoming noticeable again after a period of being hidden or dormant. It is commonly used in the context of challenges or difficulties resurfacing.

Fundamentalist extremism has been raising its head all around the world over the last couple years.
After years of peace, political unrest raised its ugly head in the region, causing concern among the population.
Just when they thought the financial crisis was over, economic instability reared its head, affecting businesses and individuals once again.
The long-standing issue of discrimination raised its ugly head when a controversial policy change was proposed.
Despite their efforts to resolve the conflict, the dispute between the neighbors reared its head with renewed intensity.