iPhone shipments are set to take another hit as workers at supplier Foxconn’s main factory engage in violent protests.

Apple is heavily reliant on Foxconn for the manufacture of its iPhone, with Foxconn’s Zhengzhou plant one of the single biggest components in that supply chain. The Zhengzhou area is responsible for such a large portion of iPhone production that it is often referred to as “iPhone City.” iPhone City has already had its share of production issues, most recently being subjected to new COVID restrictions amid a rise in cases.

According to CNN, violent protests broke out at iPhone City, stemming from what appears to be a broken promise to new workers. Foxconn launched a major recruitment drive, promising a 3,000 yuan bonus after the first 30 days, with a second 3,000 yuan bonus after the first 60 days.

New workers who were hired, however, are reporting they were told on arrival they would not receive their first bonus until March 15, long after the promised 30 days.

“The new recruits had to work more days to get the bonus they were promised, so they felt cheated,” the worker told CNN.

For its part, Foxconn blamed the confusion on “a technical error (that) occurred during the onboarding process.”

“We apologize for an input error in the computer system and guarantee that the actual pay is the same as agreed,” the company said.

In the meantime, the protests became bad enough that Foxconn promised workers 8.000 yuan if they would quit, along with another 2,000 yuan once they board outgoing buses.

While the problem appears to be on its way toward a resolution, the protests will likely result in further delays in iPhone production.